the logo of MU is now always displayed as a last resort

%

%    \begin{macrocode}

\NeedsTeXFormat{LaTeX2e}

\ProvidesPackage{beamerthemeMU}[2017/08/27]

\ProvidesPackage{beamerthemeMU}[2017/08/28]

\mode<presentation>

%    \end{macrocode}

%

%    \end{macrocode}

% \end{macro}

%

% \begin{macro}{\mubeamer@filename@logo@lastresort}

% |\mubeamer@filename@logo@lastresort| is the filename of the logo that will be

% displayed at the bottom of the title page if

% |\mubeamer@filename@logo@fallback| is not found.

%    \begin{macrocode}

\def\mubeamer@filename@logo@lastresort{%

  \mubeamer@pathname@logo mubeamer-mu-english%

    \ifmubeamer@option@gray\else

      -color%

    \fi}

%    \end{macrocode}

% \end{macro}

%

% \begin{macro}{\mubeamer@filename@label}

% |\mubeamer@filename@label| is the filename of the label that will be

% displayed at the top of all frames.

%

% \begin{macro}{\mubeamer@subroutine@includegraphics}

% |\mubeamer@subroutine@includegraphics|\oarg{\texttt{\textbackslash

% includegraphics} options}\marg{primary file name}\marg{fallback file

% name} tries to display the graphics file \meta{primary file name}. If

% \meta{primary file name} is not found, \meta{fallback file name} is tried

% instead. If neither graphics file is found, an empty box with the specified

% height is displayed.

%    \begin{macrocode}

\newcommand*\mubeamer@subroutine@includegraphics[3][]{%

  \newif\ifmubeamer@temp@recursion

% includegraphics} options}\marg{primary file name}\marg{secondary file

% name}\marg{tertiary file name} attempts to display the graphics file

% \meta{primary file name}. If \meta{primary file name} is not found,

% \meta{secondary file name} is tried instead. If \meta{secondary file name} is

% not found either, and \meta{tertiary file name} is non-empty, then

% \meta{tertiary file name} is tried. If neither graphics file is found, an

% empty box with the specified height is displayed.

%    \begin{macrocode}

\newcount\mubeamer@temp@recursion

\newcommand*\mubeamer@subroutine@includegraphics[4][]{%

  \begingroup

  \mubeamer@temp@recursiontrue

  \mubeamer@temp@recursion=0

  \patchcmd{\Gin@ii}{\Gin@esetsize}{%

    \rule{0pt}{\@ifundefined{Gin@eheight}{0pt}{\Gin@eheight}}%

    \renewcommand{\@latex@error}[2]{%

      \ifmubeamer@temp@recursion

        \mubeamer@temp@recursionfalse

        \includegraphics[#1]{#3}

      \ifnum\mubeamer@temp@recursion<2

        \advance\mubeamer@temp@recursion by 1

        \ifnum\mubeamer@temp@recursion=1

          \includegraphics[#1]{#3}

        \else

          \if\empty#4\empty\else

            \includegraphics[#1]{#4}

          \fi

        \fi

      \fi}%

    \Gin@esetsize}{}{%

      \PackageError{beamerthemeMU}%

  \mubeamer@subroutine@includegraphics%

    [height=\mubeamer@temp@length]%

    {\mubeamer@filename@label}%

    {\mubeamer@filename@label@fallback}}

    {\mubeamer@filename@label@fallback}{}}

%    \end{macrocode}

% The frame title and subtitle are displayed underneath the label.

%    \begin{macrocode}

    ]%

    {\mubeamer@filename@logo}%

    {\mubeamer@filename@logo@fallback}%

    {\mubeamer@filename@logo@lastresort}

  \vskip\mubeamer@length@margin}

%    \end{macrocode}

% Bibliography entries are preceded with the reference text (like ``[Dijkstra,