* lisp/gnus/message.el: Don't insert TAB in headers with completion.

(message-completion-function): Don't fallback on message-tab-body-function
when message-completion-alist fails to find a completion.

Fixes: debbugs:9158

lisp/gnus/ChangeLog

+2011-10-26  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+	* message.el (message-completion-function): Make sure
+	message-tab-body-function is not attempted if one of
+	message-completion-alist fails to find a completion (bug#9158).
+
 2011-10-26  Daiki Ueno  <ueno@unixuser.org>
 	* mml.el (mml-quote-region): Quote <#secure> tag.
@@ -7,7 +13,7 @@
 	* gnus-cite.el (gnus-message-citation-mode): Doc fix (in Emacs 24,
 	calling a minor mode from Lisp with nil arg enables it, so we have to
-	make the working a bit ambiguous here).
+	make the wording a bit ambiguous here).
 2011-10-18  Teodor Zlatanov  <tzz@lifelogs.com>

lisp/gnus/message.el

@@ -7888,7 +7888,11 @@ those headers."
 		(let ((mail-abbrev-mode-regexp (caar alist)))
 		  (not (mail-abbrev-in-expansion-header-p))))
       (setq alist (cdr alist)))
-    (cdar alist)))
+    (when (cdar alist)
+      (lexical-let ((fun (cdar alist)))
+        ;; Even if completion fails, return a non-nil value, so as to avoid
+        ;; falling back to message-tab-body-function.
+        (lambda () (funcall fun) 'completion-attempted)))))
 
 (eval-and-compile
   (condition-case nil