Index: includes/menu.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/menu.inc,v
retrieving revision 1.255.2.13
diff -u -p -r1.255.2.13 menu.inc
--- includes/menu.inc	19 May 2008 07:39:19 -0000	1.255.2.13
+++ includes/menu.inc	7 Jun 2008 23:10:31 -0000
@@ -1154,6 +1154,10 @@ function drupal_help_arg($arg = array())
 function menu_get_active_help() {
   $output = '';
   $router_path = menu_tab_root_path();
+  // We will always have a path unless we are on a 403 or 404.
+  if (!$router_path) {
+    return '';
+  }
 
   $arg = drupal_help_arg(arg(NULL));
   $empty_arg = drupal_help_arg();