[closed] Wie baue ich einen optional leeren Key ein?

\documentclass[a5paper, onside, automark, open=any, headsepline]{scrartcl}

\usepackage{selinput}
\SelectInputMappings{adieresis={ä},germandbls={ß}}
\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage[top=10mm]{geometry}

\usepackage{xcolor}
\usepackage{mwe}
 \pagecolor{red!42!yellow!20}
% ===============================
% Mini-Bilder im Abbildungsverzeichnis =========
 \usepackage{graphicx}
\newlength{\lofthumbsize}
\setlength{\lofthumbsize}{2em}

\newif\iflofimage
\DeclareRobustCommand*{\lofimage}[2][]{%
  \iflofimage
    $\vcenter to \lofthumbsize{\vss%
      \hbox to \lofthumbsize{\hss\includegraphics[{width=\lofthumbsize,height=\lofthumbsize,keepaspectratio=true,#1}]{#2}\hss}%
    \vss}$%
    \quad
  \fi
  \ignorespaces
}

\usepackage{xkeyval}
%%% Definition mit Keys %%%%%%%%%%%%%%%%%%%
\makeatletter
\newcommand*\IMG@figureoptions{htb}
\newcommand*\IMG@options{}
\newcommand*\IMG@file{}
\newcommand*\IMG@shorttitle{}
\newcommand*\IMG@title{}

\define@key{IMG}{figureoptions}  {\renewcommand*\IMG@figureoptions{#1}}
\define@key{IMG}{options}  {\renewcommand*\IMG@options{#1}}
\define@key{IMG}{file} {\renewcommand*\IMG@file{#1}}
\define@key{IMG}{shorttitle}{\renewcommand*\IMG@shorttitle{#1}}
\define@key{IMG}{title}{\renewcommand*\IMG@title{#1}}

\newcommand*\IMG[1][]{%
\begingroup
\setkeys{IMG}{#1}%
%\begin{figure}[\IMG@figureoptions]   % GEHT NICHT gut - Besser     htb      ???
\begin{figure}[htb]
\begin{center}
\expandafter\includegraphics\expandafter[\IMG@options]{\IMG@file}
\caption[\lofimage{\IMG@file}  \IMG@shorttitle]{\lofimage{\IMG@file}  \IMG@title}
\end{center}
\end{figure}
\endgroup
}
\makeatother
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% ===============================
% ===============================
%========
\begin{document}
%========
\lofimagetrue
\listoffigures \par
\lofimagefalse
%\vspace{0.5cm}

\section{Abschnittsname}
\IMG[file=example-image, title=fooTitel, options={width=\textwidth}, shorttitle={fooKurztitel}, figureoptions={h}]

\IMG[file=example-grid-100x100pt, title=barTitel, options={scale=0.5}, shorttitle={barKurztitel}, figureoptions={h}] 
%========
\end{document}
%========