bug#2314: Crash with word-wrap and wrap-prefix

I was trying to report a weirdness of a long wrap-prefix
with non-nil word-wrap but got a crash.

With emacs -Q, evaluate in *scratch*:

(progn
  (setq word-wrap t wrap-prefix (make-string 120 ?\s))
  (dotimes (i 25) (insert (make-string 120 ?.) "\n")))

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7f0ea59a67a0 (LWP 9334)]
0x0000000000430f3f in underlying_face_id (it=0x7fffad9d6c30) at xdisp.c:3594
3594        if (NILP (it->stack[i].string))
(gdb) bt
#0  0x0000000000430f3f in underlying_face_id (it=0x7fffad9d6c30) at xdisp.c:3594
#1  0x0000000000430d1e in handle_face_prop (it=0x7fffad9d6c30) at xdisp.c:3534
#2  0x0000000000430071 in handle_stop (it=0x7fffad9d6c30) at xdisp.c:3134
#3  0x000000000043870f in next_element_from_string (it=0x7fffad9d6c30) at xdisp.c:6270
#4  0x000000000043684a in get_next_display_element (it=0x7fffad9d6c30) at xdisp.c:5674
#5  0x0000000000452fdb in display_line (it=0x7fffad9d6c30) at xdisp.c:16597
#6  0x000000000044b617 in try_window (window=15654180, pos={charpos = 1, bytepos = 1}, check_margins=1) at xdisp.c:14054
#7  0x000000000044a1ff in redisplay_window (window=15654180, just_this_one_p=0) at xdisp.c:13677
#8  0x0000000000445cae in redisplay_window_0 (window=15654180) at xdisp.c:12272
#9  0x0000000000665594 in internal_condition_case_1 (bfun=0x445c72 <redisplay_window_0>, arg=15654180, handlers=12715829, hfun=0x445c47 <redisplay_window_error>) at eval.c:1559
#10 0x0000000000445c28 in redisplay_windows (window=15654180) at xdisp.c:12251
#11 0x0000000000444daf in redisplay_internal (preserve_echo_area=0) at xdisp.c:11827
#12 0x0000000000442c5b in redisplay () at xdisp.c:11033
#13 0x00000000005c5dd6 in read_char (commandflag=1, nmaps=2, maps=0x7fffad9d8f20, prev_event=12357345, used_mouse_menu=0x7fffad9d92e8, end_time=0x0) at keyboard.c:2703
#14 0x00000000005d2b6b in read_key_sequence (keybuf=0x7fffad9d9490, bufsize=30, prompt=12357345, dont_downcase_last=0, can_return_switch_frame=1, fix_current_buffer=1) at keyboard.c:9432
#15 0x00000000005c2b75 in command_loop_1 () at keyboard.c:1640
#16 0x000000000066540a in internal_condition_case (bfun=0x5c27db <command_loop_1>, handlers=12444417, hfun=0x5c210c <cmd_error>) at eval.c:1511
#17 0x00000000005c24fa in command_loop_2 () at keyboard.c:1357
#18 0x0000000000664de6 in internal_catch (tag=12425809, func=0x5c24e0 <command_loop_2>, arg=12357345) at eval.c:1247
#19 0x00000000005c24b4 in command_loop () at keyboard.c:1336
#20 0x00000000005c1c52 in recursive_edit_1 () at keyboard.c:951
#21 0x00000000005c1df5 in Frecursive_edit () at keyboard.c:1013
#22 0x00000000005c0269 in main (argc=2, argv=0x7fffad9d9db8) at emacs.c:1852

GNU Emacs 23.0.90 (x86_64-pc-linux-gnu) of 2009-02-12

-- 
Juri Linkov
http://www.jurta.org/emacs/