Fix bug in org-mhe.el.

Patch from Thomas Baumann.

lisp/ChangeLog

@@ -1,3 +1,7 @@
+2008-05-18  Carsten Dominik  <dominik@science.uva.nl>
+
+	* org-mhe.el (org-mhe-follow-link): Fix bug in mhe searches.
+
 2008-05-16  Carsten Dominik  <dominik@science.uva.nl>
 
 	* org-faces.el (org-column): Document how this face is being used

lisp/org-mhe.el

@@ -204,8 +204,10 @@ folders."
                      (not (org-mhe-get-message-real-folder)))
             (kill-this-buffer)
             (mh-search "+" (list "--message-id" article))))
-      (mh-search "+" (funcall mh-search-regexp-builder
-			      (list (cons 'message-id article)))))
+      (if mh-search-regexp-builder
+          (mh-search "+" (funcall mh-search-regexp-builder
+				  (list (cons 'message-id article))))
+        (mh-search "+" article)))
     (if (org-mhe-get-message-real-folder)
         (mh-show-msg 1)
       (kill-this-buffer)