Minor fix to which-func-mode

[David PONCE <david.ponce@wanadoo.fr>]

Hi,

I submit you the following patch that fixes:
"cancel-timer: Invalid timer" errors when `which-func-mode' is
disabled and you turn it off (from a program or via customization).

Regards,
David

2004-01-08  David Ponce  <david@dponce.com>

	* progmodes/which-func.el (which-function-mode): Don't cancel
	which-func-update-timer if not set.

Index: which-func.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/progmodes/which-func.el,v
retrieving revision 1.3
diff -c -r1.3 which-func.el
*** which-func.el	30 Sep 2003 12:53:26 -0000	1.3
--- which-func.el	8 Jan 2004 08:01:06 -0000
***************
*** 198,204 ****
                    (or (eq which-func-modes t)
                        (member major-mode which-func-modes))))))
      ;; Turn it off
!     (cancel-timer which-func-update-timer)
      (setq which-func-update-timer nil)
      (dolist (buf (buffer-list))
        (with-current-buffer buf (setq which-func-mode nil)))))
--- 198,205 ----
                    (or (eq which-func-modes t)
                        (member major-mode which-func-modes))))))
      ;; Turn it off
!     (when (timerp which-func-update-timer)
!       (cancel-timer which-func-update-timer))
      (setq which-func-update-timer nil)
      (dolist (buf (buffer-list))
        (with-current-buffer buf (setq which-func-mode nil)))))