with-temp-message does not remove temporal message

[Ulrich Neumerkel]

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In GNU Emacs 21.3.3 (i686-pc-linux-gnu, X toolkit)
 of 2003-11-17 on gupu.complang.tuwien.ac.at
configured using `configure  --without-toolkit-scroll-bars --prefix /usr'
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_US
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: nil

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

When there is no message in the echo area prior to invoking
with-temp-message i.e. (not (current-message)) the temporal message is
not removed after finishing with-temp-message.

(defun temporal-flash-1 ()
  (interactive)
  (with-temp-message "Should be seen only for an instant 1")
  nil)

(defun temporal-flash-2 ()
  (interactive)
  (let ((current-message (current-message)))
    (message "Should be seen only for an instant 2")
    (message current-message)
    nil))

C-x C-e the following:

(progn (temporal-flash-1) (sit-for 5)) ;; bug
(progn (temporal-flash-2) (sit-for 5)) ;; ok
(progn (message "Information") (temporal-flash-1) (sit-for 5)) ;; ok
(progn (message "Information") (temporal-flash-2) (sit-for 5)) ;; ok