Error raised with simplest custom line style not using \par

[jfbu]

Document using

\etocsetstyle{section}
  {}
  {\etocname, }% no error if a \par here
  {}
  {}% no error if a \par here

%\def\etocaftercontentshook{\par}% no error if using this

\tableofcontents
\section{foo}
\end{document}

generates on second compilation warnings then errors with

! Package tagpdf Error: The number of automatic begin (2) and end (3)
(tagpdf)                text-unit para hooks differ!