bug#18438: 24.4.50; assertion failed in bidi.c

[aidalgol]

With no apparent pattern, I am getting an "assertion failed" (which, of 
course terminates Emacs):
src/bidi.c:329: Emacs fatal error: assertion failed: UNKNOWN_BT <= type 
&& type <= NEUTRAL_ON

I am running from git master, commit 567e68d.

In GNU Emacs 24.4.50.1 (x86_64-unknown-cygwin)
 of 2014-09-09 on AGAULAND-NZCD
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking --with-w32 'CFLAGS=-O0 -ggdb''

Configured features:
XPM JPEG TIFF GIF PNG IMAGEMAGICK DBUS NOTIFY ACL GNUTLS LIBXML2 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Dired by name

Minor modes in effect:
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-spelling-mode: t
  erc-services-mode: t
  erc-ring-mode: t
  erc-networks-mode: t
  erc-netsplit-mode: t
  erc-menu-mode: t
  erc-match-mode: t
  erc-log-mode: t
  erc-list-mode: t
  erc-pcomplete-mode: t
  erc-button-mode: t
  erc-stamp-mode: t
  erc-autojoin-mode: t
  erc-autoaway-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  ido-everywhere: t
  savehist-mode: t
  display-time-mode: t
  display-battery-mode: t
  desktop-save-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t

Recent input:
y <switch-frame> M-x e r <return> M-p <return> M-p
M-p <return> <return> <return> <lwindow> C-x b f r
e <return> C-x 3 C-x b # C-x b # <return> C-x 0 C-x
3 C-x b <return> <switch-frame> <S-lwindow> M-x C-s
<return>

Recent messages:
Desktop: File "/home/agauland/message-20140910-092339" no longer 
exists.
Starting new Ispell process aspell with british dictionary...
Wrote /home/agauland/.emacs.d/emacs.desktop.lock
Desktop: 2 frames, 41 buffers restored, 1 failed to restore.
For information about GNU Emacs and the GNU system, type C-h C-a.
Connecting to localhost:7000... ...done
Logging in as 'aidalgol'...
Logging in without password
Logging in as 'aidalgol'... done
Quit

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug sendmail gnutls network-stream starttls
tls erc-track erc-spelling erc-services erc-ring erc-networks
erc-netsplit erc-menu erc-match erc-log erc-list erc-pcomplete 
pcomplete
erc-button erc-fill erc-stamp wid-edit erc-join erc-autoaway 
erc-goodies
erc erc-backend erc-compat auth-source eieio byte-opt bytecomp
byte-compile cconv eieio-core gnus-util password-cache thingatpt pp 
smex
flyspell ispell rst compile vc-git conf-mode view cc-langs cc-mode
cc-fonts cc-guess cc-menus cc-cmds jka-compr paredit vc-dispatcher
vc-svn hideshow undo-tree diff python json message dired format-spec
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mailabbrev mail-utils
gmm-utils mailheader browse-kill-ring-autoloads 
ido-ubiquitous-autoloads
info magit-autoloads git-rebase-mode-autoloads 
git-commit-mode-autoloads
paredit-autoloads smex-autoloads undo-tree-autoloads package server
cc-styles cc-align cc-engine cc-vars cc-defs appt diary-lib
diary-loaddefs cal-menu easymenu calendar cal-loaddefs advice help-fns
ido header-file find-file gtags mu cl-macs edmacro kmacro cl gv comint
ansi-color ring saveplace paren savehist avoid time battery desktop
frameset cl-loaddefs cl-lib cus-start cus-load time-date tooltip
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
w32-common-fns disp-table w32-win w32-vars tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode prog-mode 
register
page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core frame cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew
greek romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process dbusbind
gfilenotify w32 multi-tty emacs)

Memory information:
((conses 16 308313 29216)
 (symbols 48 34000 0)
 (miscs 40 174 713)
 (strings 32 76196 4962)
 (string-bytes 1 2139625)
 (vectors 16 31311)
 (vector-slots 8 629615 26163)
 (floats 8 155 237)
 (intervals 56 11960 548)
 (buffers 976 58))