? drupal-704158-D6.patch
Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.892.2.19
diff -u -p -r1.892.2.19 user.module
--- modules/user/user.module	6 Nov 2009 07:36:34 -0000	1.892.2.19
+++ modules/user/user.module	4 Feb 2010 01:43:14 -0000
@@ -2132,7 +2132,7 @@ function user_mail_tokens($account, $lan
  */
 function user_preferred_language($account, $default = NULL) {
   $language_list = language_list();
-  if ($account->language && isset($language_list[$account->language])) {
+  if (isset($account->language) && $account->language && isset($language_list[$account->language])) {
     return $language_list[$account->language];
   }
   else {