fix: sort out utf lib name;

fix problem of throwing error when pan
the move, saying problem with the nearest arrow or tile unload process;

package.json

@@ -11,14 +11,14 @@
     "@testing-library/user-event": "^7.1.2",
     "expect-runtime": "^0.4.0",
     "leaflet": "^1.7.1",
+    "leaflet-utfgrid": "git+https://github.com/dadiorchen/Leaflet.UTFGrid.git",
     "leaflet.gridlayer.googlemutant": "^0.12.1",
     "loglevel": "^1.7.0",
     "moment": "^2.29.1",
     "react": "^16.13.1",
     "react-dom": "^16.13.1",
     "react-scripts": "3.4.1",
-    "source-map-explorer": "^2.5.0",
-    "Leaflet.UTFGrid": "git+https://github.com/dadiorchen/Leaflet.UTFGrid.git"
+    "source-map-explorer": "^2.5.0"
   },
   "scripts": {
     "start": "react-scripts start",

src/models/Map.js

@@ -882,8 +882,12 @@ export default class Map{
     }else{
       log.info("no marker");
       const nearest = await this.getNearest();
-      const placement = this.calculatePlacement(nearest);
-      this.onFindNearestAt && this.onFindNearestAt(placement);
+      if(nearest){
+        const placement = this.calculatePlacement(nearest);
+        this.onFindNearestAt && this.onFindNearestAt(placement);
+      }else{
+        log.warn("Can't get the nearest:", nearest);
+      }
     }
   }
 
@@ -894,6 +898,10 @@ export default class Map{
     const res = await this.requester.request({
       url: `${this.apiServerUrl}nearest?zoom_level=${zoom_level}&lat=${center.lat}&lng=${center.lng}`,
     });
+    if(!res){
+      log.warn("Return undefined trying to get nearest, the api return null");
+      return;
+    }
     let {nearest} = res;
     nearest = nearest? {
       lat: nearest.coordinates[1],