Fix the AddToHeightMap at the end of GenerateRailMeshes not having a collider available due to the client deferring the generation of meshes & therefore mesh colliders - still generate meshes for colliders right away on servers - generate the lowest LOD in the rare case that a client is generating a map (and not loading a cached map) - keep PathMeshLOD components disabled until procgen finishes to ensure they don't update LODs mid-map generation and start deleting the colliders