--- /etc/skel/www/includes/module.inc	2004-07-20 01:58:20.599680008 +0200
+++ module.inc	2004-07-20 02:19:11.161565704 +0200
@@ -157,7 +157,7 @@ function module_invoke_all($hook, $a1 = 
   $return = array();
   foreach (module_list() as $module) {
     $result = module_invoke($module, $hook, $a1, $a2, $a3, $a4);
-    if (isset($result)) {
+    if (is_array($result)) {
       $return = array_merge($return, $result);
     }
   }