CRM-13615 - Fix PHP error

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* CRM-13615: Implement API for Scheduled Reminders
  http://issues.civicrm.org/jira/browse/CRM-13615

CRM/Core/BAO/ActionSchedule.php

@@ -495,7 +495,7 @@ WHERE   cas.entity_value = $id AND
    * @static
    *
    */
-  static function add(&$params, &$ids) {
+  static function add(&$params, &$ids = NULL) {
     $actionSchedule = new CRM_Core_DAO_ActionSchedule();
     $actionSchedule->copyValues($params);