--- modules/filter.module	Tue Nov  1 06:00:03 2005 1.80
+++ modules/filter.module	Thu Nov  3 14:07:51 2005
@@ -563,7 +563,10 @@
   $list = filter_list_format($format);
   $form = array();
   foreach ($list as $filter) {
-    $form = array_merge($form, module_invoke($filter->module, 'filter', 'settings', $filter->delta, $format));
+    $form_module = module_invoke($filter->module, 'filter', 'settings', $filter->delta, $format);
+    if (is_array($form_module)) {
+      $form = array_merge($form, $form_module);
+    }
   }
 
   if (!empty($form)) {