unnumbered part in article is not correctly aligned.

[Udi-Fogiel]

Brief outline of the issue

Check/indicate

• Relevant to the xepersian package
• The bidi package issue tracker has been searched for similar issues?
• The xepersian package issue tracker has been searched for similar issues?
• Links to <tex.stackexchange.com> discussion if appropriate
• Links to <qa.parsilatex.com> discussion if appropriate

Minimal example showing the issue

% !TEX TS-program = XeLaTeX
% !TEX encoding = UTF-8 Unicode
\documentclass{article}
\usepackage[RTLdocument]{bidi}
\begin{document}
\part{Test}
\part*{Test}
\end{document}

Expected behavior

Both titles should be aligned the same.

Should be fixed by #28