[luatex] [texhax] Black box in math mode with LuaLaTeX + koma script

[Martin Schröder]

2013/5/31 Stefan Löffler <stefan.loeffler at tuwien.ac.at>:
> I just stumbled over the following peculiar problem: When typesetting the
> following minimal example,
>
>
> \documentclass{scrreprt}
>
> \pagestyle{empty}
>
> \begin{document}
>
> \[
>
> \sqrt{\sum_i \Bigg(}
>
> \]
>
> \end{document}
>
>
> with LuaLaTeX, the square root symbol is typeset above the rest of the math,
> with a large black box inside. This is reproducible with all koma script
> documentclasses. When switching to "article", using pdfLaTeX, or replacing
> \Bigg( by something smaller, the formula is typeset as it should be.
>
> Can someone reproduce this / tell me what the problem is / tell me how to
> fix this?

Reproduced. Let's continue this on the luatex list.

Best
   Martin