Don't try to make a model for tiles without any buildings - Prevents error: "Uncaught TypeError: Cannot read property 'vertexNormals' of undefined" - Skips some unnecessary code and a worker thread
Don't try to make a model for tiles without any buildings
- Prevents error: "Uncaught TypeError: Cannot read property 'vertexNormals' of undefined"
- Skips some unnecessary code and a worker thread

Error occurred on tiles like this:
http://vector.mapzen.com/osm/buildings/15/9646/12317.json

UDST/vizicities,vizicities/vizicities,marks/vizicities,UDST/vizicities,marks/vizicities,dyh333/vizicities,dyh333/vizicities