[Tex/LaTex] How to remove headerline from title and outline pages in beamer

Question

I am preparing a presentation with Beamer (theme Warsaw), I want to remove just the header line (keep the footer line) from title page and outline page. can you help me please ?

The code source created by Lyx is :

% LyX 2.1.2 created this file.  For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.
\documentclass[french]{beamer}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\setcounter{secnumdepth}{3}
\setcounter{tocdepth}{1}

\makeatletter
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Textclass specific LaTeX commands.
 % this default might be overridden by plain title style
 \newcommand\makebeamertitle{\frame{\maketitle}}%
 % (ERT) argument for the TOC
 \AtBeginDocument{%
   \let\origtableofcontents=\tableofcontents
   \def\tableofcontents{\@ifnextchar[{\origtableofcontents}{\gobbletableofcontents}}
   \def\gobbletableofcontents#1{\origtableofcontents}
 }


\usetheme{Warsaw}

\usepackage{multicol}
\date{}

\usepackage{babel}
\makeatletter
\addto\extrasfrench{%
   \providecommand{\og}{\leavevmode\flqq~}%
   \providecommand{\fg}{\ifdim\lastskip>\z@\unskip\fi~\frqq}%
}

\makeatother
\begin{document}

\title[]{Title page}


\author[Jeudi $14$ Juillet $2016$]{Nejib MEDIOUNI\\
}

\makebeamertitle

\newcommand*\oldmacro{}%
\let\oldmacro\insertshorttitle%
\renewcommand*\insertshorttitle{%
  \oldmacro\hfill% 
 \insertframenumber\,/\,\inserttotalframenumber}


\begin{frame}{Plan}


\tableofcontents{} [pausesections]


\end{frame}

\section{Section 1}


\section{Section 2}
\begin{frame}{Title frame}


test test test
\end{frame}

\end{document}

Answer 1

You can temporarily redefine the headline, if you put the redefinition and the frame within a group or {}:

\documentclass[french]{beamer}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\usepackage[french]{babel}
\setcounter{secnumdepth}{3}
\setcounter{tocdepth}{1}
\usetheme{Warsaw}

\makeatletter
% (ERT) argument for the TOC
\AtBeginDocument{%
    \let\origtableofcontents=\tableofcontents
    \def\tableofcontents{\@ifnextchar[{\origtableofcontents}{\gobbletableofcontents}}
    \def\gobbletableofcontents#1{\origtableofcontents}
}

\addto\extrasfrench{%
    \providecommand{\og}{\leavevmode\flqq~}%
    \providecommand{\fg}{\ifdim\lastskip>\z@\unskip\fi~\frqq}%
}
\makeatother

\newcommand*\oldmacro{}%
\let\oldmacro\insertshorttitle%
\renewcommand*\insertshorttitle{%
    \oldmacro\hfill% 
    \insertframenumber\,/\,\inserttotalframenumber}

\title[]{Title page}
\author[Jeudi $14$ Juillet $2016$]{Nejib MEDIOUNI}
\date{}

\begin{document}

\begingroup 
    \setbeamertemplate{headline}{}
    \begin{frame}
        \titlepage
    \end{frame}
\endgroup

\begingroup 
    \setbeamertemplate{headline}{}
    \addtobeamertemplate{frametitle}{\vspace*{-\headheight}}{}
    \begin{frame}{Plan}
        \tableofcontents{} [pausesections]
    \end{frame}
\endgroup

    \section{Section 1}

    \section{Section 2}
    \begin{frame}{Title frame}  
        test test test
    \end{frame}

\end{document}