tile
The protomaps tile server responds with an HTTP 204 (No Content), and no body, for tiles that have no data at all, e.g. remote areas with no OSM features nearby. Note this is not the same as a tile that's entirely open sea, or one with a layer present but no features in it - those are still served normally with an HTTP 200. Retrofit special cases a 204/205 response and always returns a null body for it, even though the tile request itself succeeded, so that has to be turned back into an empty VectorTile here rather than being treated as a failed request that's worth retrying.