bug#30705: Segfault in get_next_display_element

[Eli Zaretskii]

> From: Clément Pit-Claudel <clement.pitclaudel@live.com>
> Date: Sun, 4 Mar 2018 17:37:26 -0500
> 
> A user of one of my packages reported 
> (https://github.com/cpitclaudel/company-coq/issues/159) a segfault in 
> get_next_display_element, and collected the following information:
> [...]
> * thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS 
> (code=2, address=0x7fff5f3aefd8)
>   * frame #0: 0x0000000100018e58 Emacs`get_next_display_element + 44
>     frame #1: 0x000000010001988e Emacs`get_next_display_element + 2658.
> ...  (these are all identical)
>     frame #60207: 0x000000010001988e Emacs`get_next_display_element + 2658.

This is bug#27661, already fixed in Emacs 26.  I suggest that this
user upgrades to the latest pretest of 26.1.

Thanks.