bug#27761: Crash while using proof-general/company-coq on OS X

[Eli Zaretskii <eliz@gnu.org>]

> From: Денис Редозубов <denis.redozubov@gmail.com>
> Date: Thu, 3 Aug 2017 11:10:01 +0300
> Cc: John Wiegley <jwiegley@gmail.com>, 27761@debbugs.gnu.org, 
> 	"Charles A. Roelli" <charles@aurox.ch>
> 
> (gdb) p *$12
> $13 = {
>   size = 4,
>   size_byte = -1,
>   intervals = 0x102a31430,
>   data = 0x11433f500 " 163"
> }
> (gdb) up
> #10438 0x00000001000393d4 in get_next_display_element (it=0x7fff5fbd5bb0)
>     at xdisp.c:7324
> 7324      success_p = get_next_display_element (it);
> (gdb) p it->current
> $14 = {
>   pos = {
>     charpos = 4138,
>     bytepos = 4138
>   },
>   overlay_string_index = -1,
>   string_pos = {
>     charpos = 6,
>     bytepos = 6
>   },
>   dpvec_index = -1
> }
> (gdb) p it->sp
> $15 = 2
> (gdb) p it->string
> $16 = Python Exception <type 'exceptions.AttributeError'> 'NoneType' object
> has no attribute 'value':
> 
> (gdb) xstring
> $17 = (struct Lisp_String *) 0x10da1ee10
> " 163"

Thanks, we are making progress.  A few more requests:

  (gdb) p it->stop_charpos
  (gdb) p it->end_charpos
  (gdb) p it->stack[1].string
  (gdb) xstring
  (gdb) p it->stack[1].current
  (gdb) p it->stack[1].stop_charpos
  (gdb) p it->stack[1].end_charpos
  (gdb) p it->stack[1].method