bug#29031: 25.3; Segmentation fault when starting emacs with my config

[Eli Zaretskii]

> From: Kaushal Modi <kaushal.modi@gmail.com>
> Date: Mon, 30 Oct 2017 18:34:22 +0000
> Cc: 29031@debbugs.gnu.org
> 
> (gdb) p glyph
> $1 = (struct glyph *) 0x8f
> (gdb) p glyph->charpos
> Cannot access memory at address 0x8f

So the problematic data is 'glyph'.  What do the following print?

  (gdb) p it->area
  (gdb) p it->glyph_row
  (gdb) p it->glyph_row->used[area]