bug#9545: 24.0.50; Bidi-related crash under selective display

[Chong Yidong]

emacs -Q
C-x C-f RET
[Move point to a line listing a subdirectory]
$

(gdb) bt
#0  abort () at emacs.c:386
#1  0x00000000004d8a59 in bidi_cache_iterator_state (bidi_it=0x7fffffff7700,
    resolved=1) at bidi.c:533
#2  0x00000000004dcad6 in bidi_move_to_visually_next (bidi_it=0x7fffffff9b78)
    at bidi.c:2272
#3  0x000000000043ea50 in set_iterator_to_next (it=0x7fffffff91d0, reseat_p=0)
    at xdisp.c:6679
#4  0x000000000043b4e4 in forward_to_next_line_start (it=0x7fffffff91d0,
    skipped_p=0x7fffffff8278, bidi_it_prev=0x7fffffff7f00) at xdisp.c:5519
#5  0x000000000043bdb8 in reseat_at_next_visible_line_start (
    it=0x7fffffff91d0, on_newline_p=0) at xdisp.c:5730
#6  0x000000000043e6c8 in set_iterator_to_next (it=0x7fffffff91d0, reseat_p=1)
    at xdisp.c:6583
#7  0x000000000046082e in display_line (it=0x7fffffff91d0) at xdisp.c:18920
#8  0x0000000000456937 in try_window (window=16886069, pos=..., flags=1)
    at xdisp.c:15680
#9  0x0000000000454ced in redisplay_window (window=16886069, just_this_one_p=0)
    at xdisp.c:15224

In GNU Emacs 24.0.50.34 (x86_64-unknown-linux-gnu, GTK+ Version 2.20.1)
 of 2011-09-18 on furball
Windowing system distributor `The X.Org Foundation', version 11.0.10706000
configured using `configure  'CC=gcc' 'CFLAGS=-g''