bug#20977: 24.5; Hi Lock Mode fails with "Invalid pattern list expression"

[Raffaele Ricciardi <rfflrccrd@gmail.com>]

This may happen in Help buffers.

Recipe:

emacs -Q
C-h f hi-lock-mode RET
C-x b *Help* RET
M-x hi-lock-mode RET

Emacs says:

Invalid pattern list expression at 60


Thank you.

--

In GNU Emacs 24.5.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.25)
  of 2015-06-27 on debian
Windowing system distributor `The X.Org Foundation', version 11.0.11604000
System Description:    Debian GNU/Linux 8.1 (jessie)

Configured using:
  `configure --prefix=/opt/emacs/emacs-24.5-gtk2 --with-x-toolkit=gtk2'

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

Major mode: Help

Minor modes in effect:
   hi-lock-mode: t
   tooltip-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-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
   line-number-mode: t
   transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading hi-lock...done
Type C-x 1 to delete the help window, C-M-v to scroll help.
Invalid pattern list expression at 60
  [3 times]
Debug on Error enabled globally
Invalid pattern list expression at 60
Quit

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util
mail-prsvr mail-utils cus-start cus-load pp hi-lock help-mode easymenu
help-fns time-date tooltip electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel x-win x-dnd 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 dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 83092 7518)
  (symbols 48 18597 0)
  (miscs 40 50 171)
  (strings 32 11407 4465)
  (string-bytes 1 301418)
  (vectors 16 9121)
  (vector-slots 8 386170 15786)
  (floats 8 70 182)
  (intervals 56 218 9)
  (buffers 960 12)
  (heap 1024 18347 926))