Error when summary window does not exist

[Uday Reddy]

If a summary window does not exist but VM believes that it does, error traces like this arise. It would be good to recover from the error, because not even quit-no-change works any more!

Debugger entered--Lisp error: (wrong-number-of-arguments emacs-get-buffer-window 3)
  emacs-get-buffer-window(" *vm-nonexistent-summary*" nil nil)
   vm-get-buffer-window(" *vm-nonexistent-summary*")
  vm-set-window-configuration(vm-quit-no-change quitting)
  apply(vm-set-window-configuration (vm-quit-no-change quitting))
  vm-display(nil nil (vm-quit vm-quit-no-change vm-quit-no-expunge) (vm-quit-no-change quitting))
  vm-quit(t t)
  vm-quit-no-change()
  call-interactively(vm-quit-no-change nil nil)