Server is pending if tile not found (*.mvt and *.vt)

[boeckMt]

If the requested tile is null (so tileIndexes[layer].getTile(z, x, y) is not finding the tile in tileIndexes) there also should be a response not only return in the Express route otherwise the browser is stuck in a pending request.

E.g.

• https://github.com/TNOCS/geojson-tile-server/blob/master/src/server.ts#L99
• https://github.com/TNOCS/geojson-tile-server/blob/master/src/server.ts#L108

app.get("/:layer/:z/:x/:y...", (req, res) => {
    const { tile } = getTile(req, res);
    if (!tile || !tile.features) {
+     res.sendStatus(404);
      return;
    }
    ...
  });

I think this would also be good for *..geojson

• https://github.com/TNOCS/geojson-tile-server/blob/master/src/server.ts#L90

It there are no features in the title, this should maybe be extra handled mapbox/mapbox-gl-js#9304