Index: common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1120
diff -u -r1.1120 common.inc
--- common.inc	3 Mar 2010 19:55:46 -0000	1.1120
+++ common.inc	6 Mar 2010 01:37:50 -0000
@@ -5281,7 +5281,7 @@
   $children = array();
   $sortable = FALSE;
   foreach ($elements as $key => $value) {
-    if ($key[0] !== '#') {
+    if ($key !== '' && $key[0] !== '#') {
       $children[$key] = $value;
       if (is_array($value) && isset($value['#weight'])) {
         $sortable = TRUE;