* Allow `null` maps for `MeshBasicMaterial`s
A mesh can optionally have a `map` but right now this doesn't allow us to remove a material's map by setting it to `null`, which is the default value for maps.
* All textures are nullable
https://threejs.org/docs/#api/en/materials/MeshStandardMaterial
* Lots of other things are nullable, too
* Fix indentation
My editor changed the indentation of this file.. oops.
* Actually fix indentation
