CRM-12466 - Fix missing var (follow up to #927)

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* CRM-12466: Group listings don't load
  http://issues.civicrm.org/jira/browse/CRM-12466

CRM/Contact/BAO/GroupContactCache.php

@@ -169,7 +169,7 @@ AND     ( g.cache_date IS NULL OR
 
     if (!empty($refreshGroupIDs)) {
       $refreshGroupIDString = CRM_Core_DAO::escapeString(implode(', ', $refreshGroupIDs));
-      $time  = CRM_Utils_Date::getUTCTime($smartGroupCacheTimeout * 60);
+      $time  = CRM_Utils_Date::getUTCTime(self::smartGroupCacheTimeout() * 60);
       $query = "
 UPDATE civicrm_group g
 SET    g.refresh_date = $time