bug#15844: 24.3.50; Segfault in redisplay_internal

[Eli Zaretskii]

> From: Nathan Trapuzzano <nbtrap@nbtrap.com>
> Date: Sat, 09 Nov 2013 17:05:49 -0500
> 
> I'm getting an occasional segfault when attempting to display the source
> of an internal function definition through the C-x f interface.  It
                                                 ^^^^^
Did you mean "C-h f"?

> happens when accessing face->foreground where face is set to the NULL
> return value from FACE_FROM_ID in turn_on_face.

Please try to figure out how come FACE_FROM_ID returns NULL when the
face ID is 24.  (Is it always 24 when this happens?)

> #0  0x00000000004aaf75 in turn_on_face (f=0xb67300, face_id=24) at term.c:1895
>         face = 0x0
>         fg = 19676608
>         bg = 4877402
>         tty = 0x7fff8a6c41c0