bug#12251: 24.2.50; crash in note_mouse_highlight

[Eli Zaretskii]

> From: Sam Steingold <sds@gnu.org>
> Date: Tue, 21 Aug 2012 14:20:48 -0400
> 
> In GNU Emacs 24.2.50.3 (x86_64-unknown-linux-gnu, X toolkit, Xaw3d scroll 
> bars)
>  of 2012-08-20 on t520sds
> Bzr revision: 109703 rgm@gnu.org-20120820181303-1o7qqwvj2z4q4cuu
> Windowing system distributor `The X.Org Foundation', version 11.0.11103000
> Configured using:
>  `configure '--with-wide-int''
> 
> emacs just crashed for me:
> 
> Program received signal SIGSEGV, Segmentation fault.
> note_mouse_highlight (f=0x1175580, x=298, y=1012) at 
> /home/sds/src/emacs/trunk/src/xdisp.c:27710
> 27710         && w->last_modified == BUF_MODIFF (b)

The problem is with b->text:

>  text = 0x0,

whereas BUF_MODIFF needs to dereference it:

  #define BUF_MODIFF(buf) ((buf)->text->modiff)

However, ...

> #8  0x00000000004f5da5 in cmd_error_internal (data=68832822, 
> context=0x7fffffffcf30 "")
>     at /home/sds/src/emacs/trunk/src/keyboard.c:1147
> #9  0x00000000004f5f23 in cmd_error (data=68832822) at 
> /home/sds/src/emacs/trunk/src/keyboard.c:1080

what error are we trying to process here?  What is 'data' in frame #8?