rebber: array issue

[Karnaj]

+----+----+
| aa | aa |
+====+====+
| aa | aa |
+----+----+
| aa | aa |
+----+----+

This code products this LaTeX.

\begin{longtabu}{|p{\dimexpr(\linewidth) / 2}|p{\dimexpr(\linewidth) / 2}|} \hline
\rowfont[c]{\bfseries}
aa & aa \\ \hline
\rowfont[c]{\bfseries}
aa & aa \\ \hline
\rowfont[l]{}
aa & aa \\ \hline
\end{longtabu}

It should product this one.

\begin{longtabu}{|p{\dimexpr(\linewidth) / 2}|p{\dimexpr(\linewidth) / 2}|} \hline
\rowfont[c]{\bfseries}
aa & aa \\ \hline
\rowfont[l]{}
aa & aa \\ \hline
aa & aa \\ \hline
\end{longtabu}