quitting ediff with pop-up-frames non-nil gives wrong-type arg error

[Drew Adams]

emacs -q

M-x set-variable pop-up-frames t

M-x ediff-buffers

quit ediff with`y'

I get this backtrace:

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
  balance-windows()
  ediff-cleanup-mess()
  run-hooks(ediff-quit-hook)
  ediff-really-quit(nil)
  ediff-quit(nil)
  call-interactively(ediff-quit)



In GNU Emacs 22.0.50.1 (i386-mingw-nt5.1.2600)
 of 2006-03-20 on W2ONE
X server distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --cflags -Id:/g/include'

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: ENU
  locale-coding-system: cp1252
  default-enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  encoded-kbd-mode: t
  tooltip-mode: t
  auto-compression-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
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  line-number-mode: t

Recent input:
<switch-frame> <down-mouse-1> <mouse-movement> <mouse-1>
M-x e d i f f - b u f f e r s <return> <return> <return>
n q y M-x s e t - v a r - <backspace> <return> d i
e <backspace> <backspace> e b u g - o n - e r <return>
t <return> <switch-frame> <down-mouse-1> <mouse-movement>
<mouse-1> C-x <escape> <escape> M-p <return> <down-mouse-1>
<mouse-1> n <switch-frame> <switch-frame> <switch-frame>
q y <switch-frame> <switch-frame> <help-echo> <help-echo>
<help-echo> <help-echo> <switch-frame> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <menu-bar>
<help-menu> <report-emacs-bug>

Recent messages:
ediff-cleanup-mess: Wrong type argument: number-or-marker-p, nil
Computing differences between SAVE-2006-07-09b-icicles-fn.el and
icicles-fn.el ...
Buffer A: Processing difference region 0 of 3
Buffer B: Processing difference region 0 of 3
Processing difference regions ... done
Refining difference region 1 ...
Quit this Ediff session? (y or n)
Loading debug...done
Entering debugger...
Loading emacsbug...done