Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.349
diff -u -r1.349 form.inc
--- includes/form.inc	7 Jul 2009 22:32:17 -0000	1.349
+++ includes/form.inc	16 Jul 2009 03:42:34 -0000
@@ -1421,14 +1424,16 @@
  */
 function _form_set_value(&$form_values, $element, $parents, $value) {
   $parent = array_shift($parents);
-  if (empty($parents)) {
-    $form_values[$parent] = $value;
-  }
-  else {
-    if (!isset($form_values[$parent])) {
-      $form_values[$parent] = array();
+  if (is_array($form_values)) {
+    if (empty($parents)) {
+      $form_values[$parent] = $value;
+    }
+    else {
+      if (!isset($form_values[$parent])) {
+        $form_values[$parent] = array();
+      }
+      _form_set_value($form_values[$parent], $element, $parents, $value);
     }
-    _form_set_value($form_values[$parent], $element, $parents, $value);
   }
 }