Ensure bridges exist when trying to determine bridged parties when publishing transfer information.

........

Merged revisions 420387 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@420388 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/bridge.c

@@ -3949,8 +3949,12 @@ static void stasis_publish_data_init(struct ast_channel *to_transferee,
 		publication->to_transfer_target.bridge = to_target_bridge;
 	}
 
-	publication->transferee_channel = ast_bridge_peer(to_transferee_bridge, to_transferee);
-	publication->target_channel = ast_bridge_peer(to_target_bridge, to_transfer_target);
+	if (to_transferee_bridge) {
+		publication->transferee_channel = ast_bridge_peer(to_transferee_bridge, to_transferee);
+	}
+	if (to_target_bridge) {
+		publication->target_channel = ast_bridge_peer(to_target_bridge, to_transfer_target);
+	}
 }
 
 /*