ws时，删除最后一个实时轨迹，会清空图层问题

src/stores/ship-map/ship-map.ts

@@ -127,6 +127,7 @@ export const useShipMapStore = defineStore('shipMap', () => {
               state.ws.instance = null
               state.map.removeLayer(state.ws.layerShip)
               state.ws.layerShip = null
+              switchZoom()
             } else {
               initWebSocket()
             }