- if (isset($conversation['protocol']) && isset($conversation['source']) && ($old_conv['protocol'] < $conversation['protocol'])
- && ($old_conv['protocol'] != 0) && ($old_conv['protocol'] != self::PARCEL_ACTIVITYPUB)) {
+ if (empty($conversation['source']) || (!empty($old_conv['source']) &&
+ ($old_conv['protocol'] < defaults($conversation, 'protocol', PARCEL_UNKNOWN)))) {