How to remove vertical-line gap on right side of tables when adding space between header and content?

Question

I use the supertabular environment to create a table containing images. I defined that the header should be separated from the content by a single line. Because the first image in table is on the line separating header from content, I have added a space with \\[0.5em] (see MWE). The problem I have is, that the right vertical line of my table now is broken. All other vertical lines are ok. If I remove the space everything is fine, but the image aligns directly to the header line.

How to get the gap on the right vertical line under the table header closed?

Image illustrating problem:

MWE with gap:

\documentclass[a4paper,12pt,ngerman]{scrreprt}

\usepackage{supertabular}
\usepackage{graphicx}
\usepackage{array}

\begin{document}
\tablefirsthead{\hline\textsc{grafische Notation }& \textsc{Bedeutung} \\\hline \\[0.5em]}
\tablehead{\hline\textsc{grafische Notation }& \textsc{Bedeutung} \\\hline \\[0.5em]}
\tabletail{
\hline
\multicolumn{2}{|r|}{\small Fortsetzung auf nächster Seite}
\\
}
\tablelasttail{\hline}

\begin{supertabular}{|m{0.3\textwidth}|m{0.65\textwidth}|}

\centering  \includegraphics[width=0.25\textwidth]{tex}  &
{ bla}
\\

\centering  \includegraphics[width=0.25\textwidth]{tex}  &
blub\\
\end{supertabular}
\end{document}

MWE without gap:

\documentclass[a4paper,12pt,ngerman]{scrreprt}

\usepackage{supertabular}
\usepackage{graphicx}
\usepackage{array}

\begin{document}
\tablefirsthead{\hline\textsc{grafische Notation }& \textsc{Bedeutung} \\\hline}
\tablehead{\hline\textsc{grafische Notation }& \textsc{Bedeutung} \\\hline}
\tabletail{
\hline
\multicolumn{2}{|r|}{\small Fortsetzung auf nächster Seite}
\\
}
\tablelasttail{\hline}

\begin{supertabular}{|m{0.3\textwidth}|m{0.65\textwidth}|}

\centering  \includegraphics[width=0.25\textwidth]{tex}  &
{ bla}
\\

\centering  \includegraphics[width=0.25\textwidth]{tex}  &
blub\\
\end{supertabular}
\end{document}

Answer 1

you create empty lines after your head settings which is in general not a good idea.

... \\[0.5cm]

this empty tabular line is finished just right after the first column, the reason why the right vertival line isn't drawn. Use:

\tablefirsthead{\hline\textsc{grafische Notation }& \textsc{Bedeutung} \\\hline 
  ~& ~\\[0.5em]}


However, using something like \rule[-1ex]{0pt}{3ex} to get some vertical space in the tabular line makes more sense