bug#33889: 27.0.50; Segfault in directory-files

[Eli Zaretskii]

> From: Richard Copley <rcopley@gmail.com>
> Date: Thu, 27 Dec 2018 15:35:41 +0000
> 
> Recipe from 'emacs -Q':
> M-: (directory-files "." nil t) RET
> 
> Expected result: wrong-type-argument error is signaled.
> Actual result: access violation, backtrace below (non-printable
> characters replaced with ".").

Thanks, should be fixed now.