[core] update the modified/expires debug info for unmodified responses as well

src/mbgl/map/vector_tile_data.cpp

@@ -41,6 +41,9 @@ VectorTileData::VectorTileData(const TileID& id_,
         // messages from being displayed again, e.g. after a connection trouble cleared up.
         error = nullptr;
 
+        modified = modified_;
+        expires = expires_;
+
         if (!tile) {
             // This is a 404 response. We're treating these as empty tiles.
             state = State::parsed;
@@ -55,9 +58,6 @@ VectorTileData::VectorTileData(const TileID& id_,
             state = State::partial;
         }
 
-        modified = modified_;
-        expires = expires_;
-
         // Kick off a fresh parse of this tile. This happens when the tile is new, or
         // when tile data changed. Replacing the workdRequest will cancel a pending work
         // request in case there is one.