--- sites/all/modules/realname_userreference/realname_userreference.module	2010-06-29 17:21:33.000000000 -0500
+++ sites/all/modules/realname_userreference/PATCHrealname_userreference.module	2010-06-29 17:24:03.000000000 -0500
@@ -428,17 +428,19 @@ function _realname_userreference_potenti
  * Menu callback; Retrieve a pipe delimited string of realname autocomplete suggestions for existing users
  */
 function realname_userreference_auto($field_name, $string = '') {
-  $fields = content_fields();
-  $field = $fields[$field_name];
-  $match = isset($field['widget']['autocomplete_match']) ? $field['widget']['autocomplete_match'] : 'contains';
-  $matches = array();
+  if (!empty($field_name)) {
+    $fields = content_fields();
+    $field = $fields[$field_name];
+    $match = isset($field['widget']['autocomplete_match']) ? $field['widget']['autocomplete_match'] : 'contains';
+    $matches = array();
 
-  $references = _realname_userreference_potential_references($field, $string, $match, array(), 10);
-  foreach ($references as $id => $row) {
-    // Add a class wrapper for a few required CSS overrides.
-    $matches[$row['title']] = '<div class="reference-autocomplete">'. $row['rendered'] .'</div>';
+    $references = _realname_userreference_potential_references($field, $string, $match, array(), 10);
+    foreach ($references as $id => $row) {
+      // Add a class wrapper for a few required CSS overrides.
+      $matches[$row['title']] = '<div class="reference-autocomplete">'. $row['rendered'] .'</div>';
+    }
+    drupal_json($matches);
   }
-  drupal_json($matches);
 }
 
 /**