Add test for undefined GeoJSON properties (#6873)

* Add test for undefined properties

* FIx lint

* Review comments

* Update changelog

Author: mwilsnd

CHANGELOG.md

@@ -8,6 +8,7 @@
 - Fix `LngLatBounds#intersects` returning `false` for bounds spanning 360° or more ([#6863](https://github.com/maplibre/maplibre-gl-js/pull/6863)) (by [@lucaswoj](https://github.com/lucaswoj))
 - Fix getting the right zoom for getElevationForLngLat ([#6825](https://github.com/maplibre/maplibre-gl-js/pull/6825)) (by [@HarelM](https://github.com/HarelM))
 - Fix stale transform state being applied after changing `minZoom` or `maxZoom` due to old copies from `transformCameraUpdate` taking precedence. `transformCameraUpdate` is now called from `setMinZoom` and `setMaxZoom` to allow user to control subsequent changes to `zoom` [#6766](https://github.com/maplibre/maplibre-gl-js/issues/6766) (by [@Auspicus](https://github.com/Auspicus))
+- Fix GeoJSON source throwing with undefined properties [#6730](https://github.com/maplibre/maplibre-gl-js/issues/6730) (by [@wayofthefuture](https://github.com/wayofthefuture))
 - _...Add new stuff here..._
 
 ## 5.14.0

src/source/geojson_worker_source.test.ts

@@ -8,6 +8,7 @@ import {type Actor} from '../util/actor';
 import {type WorkerTileParameters} from './worker_source';
 import {setPerformance, sleep} from '../util/test/util';
 import {type FakeServer, fakeServer} from 'nise';
+import {GEOJSON_TILE_LAYER_NAME} from '@maplibre/vt-pbf';
 
 const actor = {send: () => {}} as any as Actor;
 
@@ -66,6 +67,49 @@ describe('reloadTile', () => {
         expect(spy).toHaveBeenCalledTimes(2);
     });
 
+    test('handles null and undefined properties during tile serialization', async () => {
+        const layers = [
+            {
+                id: 'mylayer',
+                source: 'sourceId',
+                type: 'symbol',
+            }
+        ] as LayerSpecification[];
+        const layerIndex = new StyleLayerIndex(layers);
+        const source = new GeoJSONWorkerSource(actor, layerIndex, []);
+        const geoJson = {
+            'type': 'Feature',
+            'geometry': {
+                'type': 'Point',
+                'coordinates': [0, 0]
+            },
+            'properties': {
+                'nullProperty': null,
+                'undefinedProperty': undefined,
+                'stringProperty': 'string'
+            }
+        };
+        const tileParams = {
+            source: 'sourceId',
+            uid: 0,
+            tileID: new OverscaledTileID(0, 0, 0, 0, 0),
+            maxZoom: 10
+        };
+
+        await source.loadData({type: 'geojson', source: 'sourceId', data: geoJson} as LoadGeoJSONParameters);
+
+        // load vector data from geojson, passing through the tile serialization step
+        const data = await source.reloadTile(tileParams as any as WorkerTileParameters);
+        expect(data.featureIndex).toBeDefined();
+
+        // deserialize tile layers in the feature index
+        data.featureIndex.rawTileData = data.rawTileData;
+        const featureLayers = data.featureIndex.loadVTLayers();
+        expect(Object.keys(featureLayers)).toHaveLength(1);
+
+        // validate supported features are present in the index
+        expect(featureLayers[GEOJSON_TILE_LAYER_NAME].feature(0).properties['stringProperty']).toBeDefined();
+    });
 });
 
 describe('resourceTiming', () => {