treat features with empty coordinates like null geometry

src/convert.js

@@ -26,6 +26,8 @@ function convertFeature(features, geojson, options, index) {
     if (!geojson.geometry) return;
 
     const coords = geojson.geometry.coordinates;
+    if (coords && coords.length === 0) return;
+
     const type = geojson.geometry.type;
     const tolerance = Math.pow(options.tolerance / ((1 << options.maxZoom) * options.extent), 2);
     let geometry = [];

test/fixtures/empty-coords.json

@@ -0,0 +1,4 @@
+{
+    "type":"Polygon",
+    "coordinates": []
+}

test/test-full.js

@@ -37,6 +37,11 @@ test('null geometry', () => {
     assert.deepEqual({}, genTiles(getJSON('feature-null-geometry.json')));
 });
 
+test('empty coordinates', () => {
+    // should ignore features with empty coordinates
+    assert.deepEqual({}, genTiles(getJSON('empty-coords.json')));
+});
+
 function getJSON(name) {
     return JSON.parse(fs.readFileSync(new URL(`fixtures/${name}`, import.meta.url)));
 }