static _notifyCatchAllListeners (lGroup, data) {
    if (!lGroup['']) return

    for (let j = 0; j < lGroup[''].length; j++) {
      lGroup[''][j].cb(data)
    }
  }
@param {object} lGroup - listener group keyed by event ('' in this case)
@param {*} data - packet to pass to listeners
@private