bug#34256: 27.0.50; Crash on draw_glyphs()

[Eli Zaretskii]

> From: Kaushal Modi <kaushal.modi@gmail.com>
> Date: Thu, 31 Jan 2019 10:50:26 -0500
> Cc: 34256@debbugs.gnu.org
> 
>  >     img_id = 0,
> 
>  img_id = 0 is unusual for an image in a buffer.  Are you running with
>  the tool bar disabled, perhaps?
> 
> Yes, I am! I am hiding both tool and menu bars.

So if you start "emacs -Q", then disable the tool bar, perhaps you can
reproduce the problem without your elaborate setup?

>    (gdb) p FRAME_IMAGE_CACHE (s->f)->used
>    (gdb) p FRAME_IMAGE_CACHE (s->f)->images[0]
> 
>  (gdb) p FRAME_IMAGE_CACHE (s->f)->used
> $2 = 2
> (gdb) p FRAME_IMAGE_CACHE (s->f)->images[0]
> $3 = (struct image *) 0x0

OK, so something sets the image in the cache to NULL.  When you
reproduce this, is there just one frame, or more than one?