kraken: return if impacts empty
kraken: return if impacts empty

kinnou02/navitia,Tisseo/navitia,antoine-de/navitia,kadhikari/navitia,ballouche/navitia,pbougue/navitia,kinnou02/navitia,CanalTP/navitia,pbougue/navitia,kinnou02/navitia,patochectp/navitia,xlqian/navitia,kadhikari/navitia,ballouche/navitia,Tisseo/navitia,patochectp/navitia,ballouche/navitia,CanalTP/navitia,pbougue/navitia,xlqian/navitia,ballouche/navitia,Tisseo/navitia,patochectp/navitia,CanalTP/navitia,antoine-de/navitia,pbougue/navitia,patochectp/navitia,Tisseo/navitia,Tisseo/navitia,xlqian/navitia,kinnou02/navitia,CanalTP/navitia,xlqian/navitia,antoine-de/navitia,CanalTP/navitia,antoine-de/navitia,kadhikari/navitia,xlqian/navitia,kadhikari/navitia