bug#6621: Emacs crash when trying to report emacs crash

[Yair F]

I can confirm that this fix resolves the bugs (two forms I found).

Thank you,
Yair

> I found a suspicious code in Ffont_shape_gstring, and the
> attached patch will fix the bug.  Could you please try it?
> I have not yet committed it because I have not yet fully
> traced the impact of the change to the other places..
>
> === modified file 'src/font.c'
> --- src/font.c  2010-07-14 03:40:47 +0000
> +++ src/font.c  2010-07-23 12:31:43 +0000
> @@ -4492,6 +4492,8 @@
>     }
>   if (i == 3 || XINT (n) == 0)
>     return Qnil;
> +  if (XINT (n) < LGSTRING_GLYPH_LEN (gstring))
> +    LGSTRING_SET_GLYPH (gstring, XINT (n), Qnil);
>
>   glyph = LGSTRING_GLYPH (gstring, 0);
>   from = LGLYPH_FROM (glyph);
>
> ---
> Kenichi Handa
> handa@m17n.org
>