[Tex/LaTex] “! Missing $ inserted.$ \printbibliography[heading=bibintoc]” error

biblatexbibtexerrors

this is my main.tex . I am getting crazy finding where the problem is. Till a couple of hours ago everything was working well because I was putting my hands only on the "Chapter1.tex", included in the following main.tex ast you can see. And now I have this error:

! Missing $ inserted.
<inserted text>
$
l.292 \printbibliography[heading=bibintoc]
I've inserted a begin-math/end-math symbol since I think
you left one out. Proceed, with fingers crossed.
! Missing $ inserted.
<inserted text>
$
l.292 \printbibliography[heading=bibintoc]
I've inserted something that you may have forgotten.
(See the <inserted text> above.)
With luck, this will get me unwedged. But if you
really didn't forget anything, try typing `2' now; then
my insertion and my current dilemma will both disappear.
Overfull \hbox (295.04535pt too wide) in paragraph at lines 292--292
[]\T1/ppl/m/n/10.95 Wikipedia. \T1/ppl/m/it/10.95 Bidi-rec-tional scat-ter-ing
dis-tri-bu-tion func-tion\T1/ppl/m/n/10.95 .     https://en.wikipedia.org/wiki/Bidi
rectional$[]\OML/cmm/m/it/10.95     cattering[]istribution[]unction$\T1/ppl/m/n/10.
95 .

My main is the following:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Masters/Doctoral Thesis 
% LaTeX Template
% Version 2.3 (25/3/16)
%
% This template has been downloaded from:
% http://www.LaTeXTemplates.com
%
% Version 2.x major modifications by:
% Vel (vel@latextemplates.com)
%
% This template is based on a template by:
% Steve Gunn (http://users.ecs.soton.ac.uk/srg/softwaretools/document/templates/)
% Sunil Patel (http://www.sunilpatel.co.uk/thesis-template/)
%
% Template license:
% CC BY-NC-SA 3.0 (http://creativecommons.org/licenses/by-nc-sa/3.0/)
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%----------------------------------------------------------------------------------------
%   PACKAGES AND OTHER DOCUMENT CONFIGURATIONS
%----------------------------------------------------------------------------------------
\documentclass[
11pt, % The default document font size, options: 10pt, 11pt, 12pt
%oneside, % Two side (alternating margins) for binding by default, uncomment to switch to one side
%chapterinoneline,% Have the chapter title next to the number in one single line
english, % ngerman for German
singlespacing, % Single line spacing, alternatives: onehalfspacing or doublespacing
%draft, % Uncomment to enable draft mode (no pictures, no links, overfull hboxes indicated)
%nolistspacing, % If the document is onehalfspacing or doublespacing, uncomment this to set spacing in lists to single
%liststotoc, % Uncomment to add the list of figures/tables/etc to the table of contents
%toctotoc, % Uncomment to add the main table of contents to the table of contents
%parskip, % Uncomment to add space between paragraphs
%nohyperref, % Uncomment to not load the hyperref package
%headsepline, % Uncomment to get a line under the header
]{MastersDoctoralThesis} % The class file specifying the document structure

\usepackage[utf8]{inputenc} % Required for inputting international characters
\usepackage[T1]{fontenc} % Output font encoding for international characters

\usepackage{algorithm2e,mathtools} % For the pseudocode

\usepackage{float} % to use the [H] in \includegraphics
\usepackage[export]{adjustbox}  % to use the left in \includegraphics

\usepackage{palatino} % Use the Palatino font by default

\usepackage[backend=bibtex,style=numeric,natbib=true]{biblatex} % Use the bibtex backend with the authoryear citation style (which resembles APA)

\addbibresource{example.bib} % The filename of the bibliography
\usepackage[dvipsnames]{xcolor}
\usepackage[autostyle=true]{csquotes} % Required to generate language-dependent quotes in the bibliography

%----------------------------------------------------------------------------------------
%   MARGIN SETTINGS
%----------------------------------------------------------------------------------------

\geometry{
    paper=a4paper, % Change to letterpaper for US letter
    inner=2.5cm, % Inner margin
    outer=3.8cm, % Outer margin
    bindingoffset=2cm, % Binding offset
    top=1.5cm, % Top margin
    bottom=1.5cm, % Bottom margin
    %showframe,% show how the type block is set on the page
}

%----------------------------------------------------------------------------------------
%   THESIS INFORMATION
%----------------------------------------------------------------------------------------

\thesistitle{Thesis Title} % Your thesis title, this is used in the title and abstract, print it elsewhere with \ttitle
\supervisor{Dr. Ing. Jacco \textsc{Bikker}} % Your supervisor's name, this is used in the title page, print it elsewhere with \supname
\examiner{} % Your examiner's name, this is not currently used anywhere in the template, print it elsewhere with \examname
\degree{Master of Science} % Your degree name, this is used in the title page and abstract, print it elsewhere with \degreename
\author{Enrico \textsc{Ribelli}} % Your name, this is used in the title page and abstract, print it elsewhere with \authorname
\addresses{} % Your address, this is not currently used anywhere in the template, print it elsewhere with \addressname

\subject{Advanced Graphics} % Your subject area, this is not currently used anywhere in the template, print it elsewhere with \subjectname
\keywords{} % Keywords for your thesis, this is not currently used anywhere in the template, print it elsewhere with \keywordnames
\university{\href{http://www.uu.nl/en}{Utrecht University}} % Your university's name and URL, this is used in the title page and abstract, print it elsewhere with \univname
\department{\href{http://www.cs.uu.nl/}{Department of Information and Computing Sciences}} % Your department's name and URL, this is used in the title page and abstract, print it elsewhere with \deptname
\group{\href{http://www.uu.nl/en/research/game-research/about-us/participating-research-groups/virtual-worlds}{Game and Virtual Worlds group}} % Your research group's name and URL, this is used in the title page, print it elsewhere with \groupname
\faculty{\href{http://www.uu.nl/en/organisation/faculty-of-science}{Faculty of Science}} % Your faculty's name and URL, this is used in the title page and abstract, print it elsewhere with \facname

\hypersetup{pdftitle=\ttitle} % Set the PDF's title to your title
\hypersetup{pdfauthor=\authorname} % Set the PDF's author to your name
\hypersetup{pdfkeywords=\keywordnames} % Set the PDF's keywords to your keywords

\begin{document}

\frontmatter % Use roman page numbering style (i, ii, iii, iv...) for the pre-content pages

\pagestyle{plain} % Default to the plain heading style until the thesis style is called for the body content

%----------------------------------------------------------------------------------------
%   TITLE PAGE
%----------------------------------------------------------------------------------------

\begin{titlepage}
\begin{center}

{\scshape\LARGE \univname\par}\vspace{1.5cm} % University name
\textsc{\Large Master Thesis}\\[0.5cm] % Thesis type

\HRule \\[0.4cm] % Horizontal line
{\huge \bfseries \ttitle\par}\vspace{0.4cm} % Thesis title
\HRule \\[1.5cm] % Horizontal line

\begin{minipage}[t]{0.4\textwidth}
\begin{flushleft} \large
\emph{Author:}\\
\href{http://www.johnsmith.com}{\authorname} % Author name - remove the \href bracket to remove the link
\end{flushleft}
\end{minipage}
\begin{minipage}[t]{0.4\textwidth}
\begin{flushright} \large
\emph{Supervisor:} \\
\href{http://www.jamessmith.com}{\supname} % Supervisor name - remove the \href bracket to remove the link  
\end{flushright}
\end{minipage}\\[3cm]

\large \textit{A thesis submitted in fulfillment of the requirements\\ for the degree of \degreename}\\[0.3cm] % University requirement text
\textit{in the}\\[0.4cm]
\groupname\\\deptname\\[2cm] % Research group name and department name

{\large \today}\\[4cm] % Date
%\includegraphics{Logo} % University/department logo - uncomment to place it

\vfill
\end{center}
\end{titlepage}

%----------------------------------------------------------------------------------------
%   DECLARATION PAGE
%----------------------------------------------------------------------------------------

\begin{declaration}
\addchaptertocentry{\authorshipname}

\noindent I, \authorname, declare that this thesis titled, \enquote{\ttitle} and the work presented in it are my own. I confirm that:

\begin{itemize} 
\item This work was done wholly or mainly while in candidature for a research degree at this University.
\item Where any part of this thesis has previously been submitted for a degree or any other qualification at this University or any other institution, this has been clearly stated.
\item Where I have consulted the published work of others, this is always clearly attributed.
\item Where I have quoted from the work of others, the source is always given. With the exception of such quotations, this thesis is entirely my own work.
\item I have acknowledged all main sources of help.
\item Where the thesis is based on work done by myself jointly with others, I have made clear exactly what was done by others and what I have contributed myself.\\
\end{itemize}

\noindent Signed:\\
\rule[0.5em]{25em}{0.5pt} % This prints a line for the signature

\noindent Date:\\
\rule[0.5em]{25em}{0.5pt} % This prints a line to write the date
\end{declaration}

\cleardoublepage

%----------------------------------------------------------------------------------------
%   QUOTATION PAGE
%----------------------------------------------------------------------------------------

\vspace*{0.2\textheight}

\noindent\enquote{\itshape Thanks to my solid academic training, today I can write hundreds of words on virtually any topic without possessing a shred of information, which is how I got a good job in journalism.}\bigbreak

\hfill Dave Barry
\clearpage

%----------------------------------------------------------------------------------------
%   ABSTRACT PAGE
%----------------------------------------------------------------------------------------
\begin{abstract}
\rule{\textwidth}{1pt}% Horizontal line
\begin{flushright}
\huge\textit{\abstractname} \par
\bigskip
\bigskip
\end{flushright}
\addchaptertocentry{\abstractname} % Add the abstract to the table of contents

Gradient Domain Path Tracer is a modern technique recently studied and presented by Kettunen \& co. It studies how a gradient image can be rendered by using standard Monte Carlo algorithms instead of Metropolis ones, topic of previous works. By studying the current results, we first aim to reproduce the same outcomes but through our own implementation of the algorithm. As second goal of our project, if possible, we would like to improve them or at least giving hints for future work.\\
Therefore, the first part of the work requires an interpretation and understanding of what pointed out and achieved by Kettunen \& co. The same literature of the field will be summarily explained from our point of view, containing brief points about general physical based rendering and how estimating gradient image is possible. Then, we will deeply explain our implementation of the gradient-domain path tracer and the math behind it. In conclusion, we will try to face those aspects that might be matter of future work and improvements, possible drawbacks not considered in the paper and results comparison between our work and the outcomes of the original paper.


\end{abstract}

%----------------------------------------------------------------------------------------
%   ACKNOWLEDGEMENTS
%----------------------------------------------------------------------------------------

\begin{acknowledgements}
\addchaptertocentry{\acknowledgementname} % Add the acknowledgements to the table of contents

The acknowledgments and the people to thank go here, don't forget to include your project advisor\ldots

\end{acknowledgements}

%----------------------------------------------------------------------------------------
%   LIST OF CONTENTS/FIGURES/TABLES PAGES
%----------------------------------------------------------------------------------------

\tableofcontents % Prints the main table of contents

\listoffigures % Prints the list of figures

\listoftables % Prints the list of tables

%----------------------------------------------------------------------------------------
%   ABBREVIATIONS
%----------------------------------------------------------------------------------------

\begin{abbreviations}{ll} % Include a list of abbreviations (a table of two columns)

\textbf{LAH} & \textbf{L}ist \textbf{A}bbreviations \textbf{H}ere\\
\textbf{WSF} & \textbf{W}hat (it) \textbf{S}tands \textbf{F}or\\

\end{abbreviations}

%----------------------------------------------------------------------------------------
%   PHYSICAL CONSTANTS/OTHER DEFINITIONS
%----------------------------------------------------------------------------------------

\begin{constants}{lr@{${}={}$}l} % The list of physical constants is a three column table

% The \SI{}{} command is provided by the siunitx package, see its documentation for instructions on how to use it

    Speed of Light & $c_{0}$ & \SI{2.99792458e8}{\meter\per\second} (exact)\\
%Constant Name & $Symbol$ & $Constant Value$ with units\\

\end{constants}

%----------------------------------------------------------------------------------------
%   SYMBOLS
%----------------------------------------------------------------------------------------

\begin{symbols}{lll} % Include a list of Symbols (a three column table)

$a$ & distance & \si{\meter} \\
$P$ & power & \si{\watt} (\si{\joule\per\second}) \\
%Symbol & Name & Unit \\

\addlinespace % Gap to separate the Roman symbols from the Greek

$\omega$ & angular frequency & \si{\radian} \\

\end{symbols}

%----------------------------------------------------------------------------------------
%   DEDICATION
%----------------------------------------------------------------------------------------

\dedicatory{For/Dedicated to/To my\ldots} 

%----------------------------------------------------------------------------------------
%   THESIS CONTENT - CHAPTERS
%----------------------------------------------------------------------------------------

\mainmatter % Begin numeric (1,2,3...) page numbering

\pagestyle{thesis} % Return the page headers back to the "thesis" style

% Include the chapters of the thesis as separate files from the Chapters folder
% Uncomment the lines as you write the chapters

\include{Chapters/Chapter1}
%\include{Chapters/Chapter2} 
%\include{Chapters/Chapter3}
%\include{Chapters/Chapter4} 
%\include{Chapters/Chapter5} 

%----------------------------------------------------------------------------------------
%   THESIS CONTENT - APPENDICES
%----------------------------------------------------------------------------------------

\appendix % Cue to tell LaTeX that the following "chapters" are Appendices

% Include the appendices of the thesis as separate files from the Appendices folder
% Uncomment the lines as you write the Appendices

\include{Appendices/AppendixA}
%\include{Appendices/AppendixB}
%\include{Appendices/AppendixC}

%----------------------------------------------------------------------------------------
%   BIBLIOGRAPHY
%----------------------------------------------------------------------------------------

\printbibliography[heading=bibintoc]

%----------------------------------------------------------------------------------------

\end{document} 

I didn't touch at all the line:

\printbibliography[heading=bibintoc]

where it says the error is. Can you please help me understanding what causes it? thanks in advance.

EDIT:

This is the entry which is giving me troubles:

@misc{BSDF,
   Author = {Wikipedia},
   Year = {2006},
   Url={https://en.wikipedia.org/wiki/Bidirectional_scattering_distribution_function},
   Title = {Bidirectional scattering distribution function}
}

and this is the .log file with the new errors.

main.log

if I use another kind of url, like for example the URL of the following entry which is also in my bibtex file, everything is fine:

@article{Perez:2003:PIE:882262.882269,
 author = {P{\'e}rez, Patrick and Gangnet, Michel and Blake, Andrew},
 title = {Poisson Image Editing},
 journal = {ACM Trans. Graph.},
 issue_date = {July 2003},
 volume = {22},
 number = {3},
 month = jul,
 year = {2003},
 issn = {0730-0301},
 pages = {313--318},
 numpages = {6},
 url = {http://doi.acm.org/10.1145/882262.882269},
 doi = {10.1145/882262.882269},
 acmid = {882269},
 publisher = {ACM},
 address = {New York, NY, USA},
 keywords = {Poisson equation, guided interpolation, image gradient, interactive image editing, seamless cloning, selection editing},
}

Best Answer

your bibliography style is trying to print

https://en.wikipedia.org/wiki/Bidirectional_scattering_distribution_function

as text but _ is the math subscript command so generates an error if used in text, you need to make sure that your URL are either in bibliography fields that are just used for URL in which case the bibliography style can quote them suitably or if they are in general text fields use the url package and

\url{https://en.wikipedia.org/wiki/Bidirectional_scattering_distribution_function}

so that _ is made safe and sensible URL-aware line breaking is activated.