[fix] UT

Author: MyShallowTime

test/mapboxgl/overlay/symbol/MapExtendSymbolSpec.js

@@ -82,7 +82,7 @@ describe('MapExtendSymbol', () => {
         });
         map.loadSymbol("point-1", (error, symbol) => {
             expect(error).not.toBeNull();
-            expect(symbol).toBe(undefined);
+            expect(symbol).toBe(null);
         })
     });
 

test/maplibregl/overlay/symbol/MapExtendSymbolSpec.js

@@ -85,7 +85,7 @@ describe('maplibregl_MapExtendSymbol', () => {
         });
         map.loadSymbol("point-1", (error, symbol) => {
             expect(error).not.toBeNull();
-            expect(symbol).toBe(undefined);
+            expect(symbol).toBe(null);
         })
     });