[NTG-context] xrightarrow specific size issue

[Johann Birnick]

Hi there,

\starttext
$\xrightarrow[50pt]$
\stoptext

doesn't work. But it should, right? In the manual

\starttext
$\xrightarrow[50]$
\stoptext

is shown, but that doesn't work either.

Best regards,
Johann