Upgrade drupal_get_form().

includes/FeedsConfigurable.inc

@@ -205,14 +205,13 @@ abstract class FeedsConfigurable {
  *   The form method that should be rendered.
  *
  * @return
- *   Rendered config form, if available. Empty string otherwise.
+ *   Config form array if available. NULL otherwise.
  */
 function feeds_get_form($configurable, $form_method) {
   $form_state = array();
   if (method_exists($configurable, $form_method)) {
     return drupal_get_form(get_class($configurable) .'_feeds_form', $configurable, $form_method);
   }
-  return '';
 }
 
 /**