prevent thrown error when a geojson tile doesn't have any features in…

… it (#4803)

* prevent thrown error when a geojson tile doesn't have any features in it

* test empty geojson tile

src/source/tile.js

@@ -212,7 +212,8 @@ class Tile {
             this.vtLayers = new vt.VectorTile(new Protobuf(this.rawTileData)).layers;
         }
 
-        const layer = this.vtLayers._geojsonTileLayer || this.vtLayers[params.sourceLayer];
+        const sourceLayer = params ? params.sourceLayer : undefined;
+        const layer = this.vtLayers._geojsonTileLayer || this.vtLayers[sourceLayer];
 
         if (!layer) return;
 

test/unit/source/tile.test.js

@@ -48,6 +48,23 @@ test('querySourceFeatures', (t) => {
         t.end();
     });
 
+    t.test('empty geojson tile', (t) => {
+        const tile = new Tile(new TileCoord(1, 1, 1));
+        let result;
+
+        result = [];
+        tile.querySourceFeatures(result, {});
+        t.equal(result.length, 0);
+
+        const geojsonWrapper = new GeoJSONWrapper([]);
+        geojsonWrapper.name = '_geojsonTileLayer';
+        tile.rawTileData = vtpbf({ layers: { '_geojsonTileLayer': geojsonWrapper }});
+        result = [];
+        t.doesNotThrow(tile.querySourceFeatures(result));
+        t.equal(result.length, 0);
+        t.end();
+    });
+
     t.test('vector tile', (t) => {
         const tile = new Tile(new TileCoord(1, 1, 1));
         let result;