Why does where-is-internal return nil?

[Juanma Barranquero]

A question about where-is-internal and keymaps.

I'm trying to do the following:

;;;; .emacs.el contains:

(global-set-key [f12] 'ielm)
(add-hook 'ielm-mode-hook
          (lambda ()
            (define-key ielm-map
                        (where-is-internal 'ielm nil t)
                        'ignore)))

;;; end of .emacs.el

According to docs, `where-is-internal' should be searching in "all the
currently active keymaps", because KEYMAP is nil.

Now:

  emacs     => we're on *scratch*
  f12       => ielm starts
  C-x k RET => ielm buffer deleted, we're back on *scratch*
  f12       => "Wrong type argument: arrayp, nil"

Somehow, on the second call, `where-is-internal' is returning nil. It
doesn't happen if I pass `global-map' to KEYMAP instead of nil, but that
means that, on the second call, `where-is-internal' is looking... where?

                                                           /L/e/k/t/u