bug#27504: 25.1; segfault when org-ellipsis is empty

[Eli Zaretskii]

> From: npostavs@users.sourceforge.net
> Date: Tue, 27 Jun 2017 08:10:58 -0400
> Cc: 27504@debbugs.gnu.org
> 
> > (setq org-ellipsis "") C-x C-e
> > (org-mode)  C-x C-e
> > * asd
> > ** def C-p tab  < and boom
> 
> I can confirm also with emacs-master.  Below is some debug info, it
> looks like next_element_from_display_vector assumes a non-empty ellipsis
> display string.
> 
> Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
> 0x00000000005823a3 in GLYPH_CODE_P (gc=XIL(0x3)) at 
> ../../emacs-master/src/dispextern.h:1872
> 1872            ? (CHARACTERP (XCAR (gc))
> (gdb) bt
> #0  0x00000000005823a3 in GLYPH_CODE_P (gc=XIL(0x3)) at 
> ../../emacs-master/src/dispextern.h:1872
> #1  0x00000000004552b0 in next_element_from_display_vector 
> (it=0x7fffffff8dc0) at ../../emacs-master/src/xdisp.c:7760

Thanks, should be fixed now.