\genfrac fails with some delimiters (e.g., <>)

Created by: PeterLuschny

Hi!

\begin{equation}
\sum_{k=0}^n (-1)^k \genfrac < > {0pt}{}{n}{k} = \frac{4^{n+1}-2^{n+1}}{n+1} B_{n+1},
\end{equation}

worked until yesterday, today we have

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <merror>
    <mtext>\begin{equation}
\sum_{k=0}^n&#xA0;(-1)^k&#xA0;\genfrac&#xA0;&lt;&#xA0;&gt;&#xA0;{0pt}{}{n}     {k}&#xA0;=&#xA0;\frac{4^{n+1}-2^{n+1}}{n+1}&#xA0;B_{n+1},
\end{equation}</mtext>
  </merror>
</math>

Regards Peter Luschny