bug#19596: 25.0.50; Crash on mouse click when menu is poped.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 14 Jan 2015 20:40:59 +0800
> From: Chris Zheng <chriszheng99@gmail.com>
> 
> On Windows with git master I experienced crashes when I use AUCTeX, and
> I think I find a simple way to reproduce it:
> 
> 1. Start Emacs with `-Q';
> 2. Left-click on `Lisp interaction' on mode line;
> 3. Move mouse cursor to the first item `Complete Lisp Symbol', and it
> will be highlighted.
> 4. Move mouse cursor out of the poped menu, left-click on main frame of
> Emacs, and it will crash with
> 
> Program received signal SIGSEGV, Segmentation fault.
> re_search_2 (bufp=0x40063a878 <searchbufs+2552>, str1=0x0, size1=0, 
> str2=0x6e006f00690074 <Address 0x6e006f00690074 out of bounds>, 
> size2=32651569749622816, startpos=0, range=0, regs=0x0, 
> stop=32651569749622816) at regex.c:4411
> 4411 buf_ch = STRING_CHAR (d);

Thanks, I fixed this on master.

(Please in the future try reporting the bug from the same build where
you encountered it, otherwise the information collected by
report-emacs-bug is not really helpful for bug resolution.)