[Bug] Prevent building a parking lot on an already built parking lot

Hello!

Currently, it's possible to build a parking lot on top of an already built parking lot, which isn't quite right — this probably needs to be fixed.

In this case for forklifts, the extra clipping is not so bad! = ) though it would be nice if i could hide the white lines.—I also wish the paved parking did not delete the surface under neath its placement tile