Issue #1161810: Fixed declaration of FeedsSource::instance() should be...

Issue #1161810: Fixed declaration of FeedsSource::instance() should be compatible with that of FeedsConfigurable::instance().

includes/FeedsSource.inc

@@ -182,7 +182,7 @@ class FeedsSource extends FeedsConfigurable {
    * Instantiate a unique object per class/id/feed_nid. Don't use
    * directly, use feeds_source() instead.
    */
-  public static function instance($importer_id, $feed_nid = 0) {
+  public static function instance($importer_id, $feed_nid) {
     $class = variable_get('feeds_source_class', 'FeedsSource');
     static $instances = array();
     if (!isset($instances[$class][$importer_id][$feed_nid])) {