Index: includes/theme.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/theme.inc,v
retrieving revision 1.415.2.24
diff -u -p -r1.415.2.24 theme.inc
--- includes/theme.inc	18 Jun 2009 12:04:04 -0000	1.415.2.24
+++ includes/theme.inc	17 Sep 2009 00:52:15 -0000
@@ -613,6 +613,10 @@ function theme() {
     include_once($include_file);
   }
   if (isset($info['function'])) {
+    if (count($args) < count($info['arguments'])) {
+      // If any arguments are missing, use the defaults provided by the hook definition.
+      $args = array_merge($args, array_slice(array_values($info['arguments']), count($args)));
+    }
     // The theme call is a function.
     $output = call_user_func_array($info['function'], $args);
   }