Proof title should add full stop only if title doesn't have it already

[nschloe]

MWE:

\documentclass{article}
\usepackage{amsthm}

\begin{document}
\begin{proof}[x]
\end{proof}

\begin{proof}[x.]
\end{proof}

\begin{proof}[x..]
\end{proof}
\end{document}

LaTeX output:

x.
x.
x..

LaTeXML output:

<document xmlns="http://dlmf.nist.gov/LaTeXML">
  <resource src="LaTeXML.css" type="text/css"/>
  <resource src="ltx-article.css" type="text/css"/>
  <proof>
    <title class="ltx_runin" font="italic">x.</title>
    <para xml:id="p1">
      <p>∎</p>
    </para>
  </proof>
  <proof>
    <title class="ltx_runin" font="italic">x..</title> <!--Wrong!-->
    <para xml:id="p2">
      <p>∎</p>
    </para>
  </proof>
  <proof>
    <title class="ltx_runin" font="italic">x…</title> <!--Wrong!-->
    <para xml:id="p3">
      <p>∎</p>
    </para>
  </proof>
</document>