[Tex/LaTex] Error: Missing } inserted. \end{center} (followed by: )

errorstables

I'm getting this error message in a document, which contains three tables.

Error: Missing } inserted. \end{center} (followed by: )

I have no idea why, I reviewed it like ten times, but might overvlook something. Have a look at my code:

\documentclass[a4paper]{article}

\usepackage[german]{babel}
\usepackage[utf8]{inputenc}
\usepackage[margin={2cm,2cm}]{geometry}
\usepackage{color, colortbl}

\title{Addendum \\ Beispieldatenbanken}
\author{}
\date{}

\definecolor{Gray}{gray}{0.9}

\begin{document}

\setlength{\parindent}{0pt}
\maketitle

\section{Kunden}
    \begin{center}
        \tiny
        \bgroup
        \def\arraystretch{1.5}
        \begin{tabular}{|l|l|l|l|l|}
            \hline
            \rowcolor{Gray}
            KNr & Name & Stadt & Saldo & Rabatt \\ 
            \hline
            1 & Legrand & Genf & -1080,00 & 0.10 \\
            \hline
            2 & Mart & Basel & -800,00 & 0.20 \\
            \hline
            3 & Frei & Basel & 0,00 & 0.10 \\
            \hline
            4 & Janvier & Genf & 0,00 & 0.10 \\
            \hline
            5 & Rosi & Lugano & 0,00 & 0.05 \\
            \hline
            6 & Meier & Z"urich & -3800,00 & 0.05 \\
            \hline
        \end{tabular}
    \end{center}

\section{Produkte}

    \begin{center}
        \tiny
        \bgroup
        \def\arraystretch{1.5}
        \begin{tabular}{|l|l|l|l|l|l|}
            \hline
            \rowcolor{Gray}
            Pnr & Bez & Gewicht & Preis & Lagerort & Vorrat \\ 
            \hline
            1 & Papier & 2000 & 20.00 & Basel & 10000 \\
            \hline
            2 & Platte & 1000 & 2500.00 & Z"urich & 400 \\
            \hline
            3 & Drucker & 5000 & 2000.00 & Genf & 200 \\
            \hline
            4 & Bildschirm & 5000 & 3000.00 & Genf & 80 \\
            \hline
            5 & CDs & 0.500 & 20.00 & Basel & 5000 \\
            \hline
            6 & Maus & 0.250 & 100.00 & Basel & 200 \\
            \hline
            7 & Speicher & 0.100 & 200.00 & Bern & 2000 \\
            \hline
        \end{tabular}
    \end{center}

        (...) % two other tables of the same form

    \end{document}

This error message appears at every \end{center} line. How can I fix this?

Best Answer

Remove the spurious \bgroup at the beginning of the table. It translates into { which has then no counterpart.

As well, I have to say a note about \tiny: modifying font size to fit a table in a given space is a very bad idea. I recommend you to look at the rotating package.