[metapost] [tex-live] mpost assertion failure

[Akira Kakuto]

Dear Werner LEMBERG,

> [This is the i386-linux 2013 binary of mpost, version 1.802,
> TeXLive SVN rev. 30584]
>
> I've just got this while processing lilypond's fonts:
>
>  mpost: ../../../texk/web2c/mplibdir/mp.w:2968:
>   mp_free_value_node: Assertion `p->has_number==2' failed.
>
> Attached are the input files to reproduce the assertion.  Note that
> the code has always worked without any problems.