bug#60815: 28.2; Hard-coded M-sff key binding in dired-aux.el

[Evgeni Pandurski]

I have set "(dired-isearch-filenames t)", and have rebound "M-s" to
something that is not a keymap (other-window). The problem appears
when I try to "isearch" in a Dired buffer. Then the following code:

(defun dired-isearch-filenames-end ()
  "Clean up the Dired file name search after terminating isearch."
  (define-key isearch-mode-map "\M-sff" nil)
  (dired-isearch-filenames-mode -1)
  (remove-hook 'isearch-mode-end-hook #'dired-isearch-filenames-end t)
  (unless isearch-suspended
    (kill-local-variable 'dired-isearch-filenames)))

runs and fails, because it can not bind to "M-sff". It works when I
change "M-sff" to something that starts with a keymap-binding. This is
also a problem in Emacs 27.