bug#490: 23.0.60; color-theme breaks input in *shell* buffer

[robert marshall <robert.marshall@tnei.co.uk>]

Downloaded color-theme from http://download.gna.org/color-theme/
(and added the directory to the load path and compiled the elc)

If I then start a freshly built emacs from cvs and 
M-x shell
M-x load-library color-theme
M-x color-theme-select
select a theme and then click the quit 'button'
which takes you back to *shell* typing pwd (or indeed anything) 
at a shell prompt (and return) will produce no output and an error
message in the echo area:

comint-snapshot-last-prompt: Wrong type argument: integer-or-marker-p, nil

where it is attempting:

  add-text-properties(nil nil (font-lock-face comint-highlight-prompt))


In GNU Emacs 23.0.60.3 (i686-pc-linux-gnu, GTK+ Version 2.12.9)
 of 2008-06-27 on rajm-laptop
Windowing system distributor `The X.Org Foundation', version 11.0.10400090
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  shell-dirtrack-mode: t
  recentf-mode: t
  show-paren-mode: t
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<escape> x s h e l l <return> <escape> x l o a d - 
l i b <return> c o l o r - t h <tab> <return> <escape> 
x c o l o r - t h <tab> s <tab> e <tab> <return> <down-mouse-2> 
<mouse-2> <down-mouse-2> <mouse-2> p w d <return> <escape> 
x s e t - v a r <return> d e b u g - o n <tab> e <tab> 
<return> t <return> <return> <help-echo> <help-echo> 
<down-mouse-2> <mouse-2> <help-echo> <help-echo> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<up> <up> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <menu-bar> 
<help-menu> <send-emacs-bug-report>

Recent messages:
Cleaning up the recentf list...done (0 removed)
Preparing diary...
No diary entries for Friday, 27 June 2008
Loading color-theme...done
Making completion list...
Loading /home/rajm/elisp/color-theme-6.6.0/themes/color-theme-example.el (source)...done
Loading /home/rajm/elisp/color-theme-6.6.0/themes/color-theme-library.el (source)...done
comint-snapshot-last-prompt: Wrong type argument: integer-or-marker-p, nil
Entering debugger...
Loading vc-cvs...done