\def\cals@issue@rowsep@alone{}
\def\cals@issue@rowsep{}
\def\cals@issue@row{}

%
% Check that there are no unneeded whitespace in output
%

\setbox0=\vbox{

\begin{calstable}

\colwidths{{100pt}{200pt}}

\brow{}
 \cell{aaaaa} \nullcell{ltb}  \nullcell{rtb}  \spancontent{bbbbb}  \cell{bbbb}  \erow{}  % ok
\end{calstable}

}

\showbox0