Fixes colors for upside down half slabs.
Fixes colors for upside down half slabs.

Zahl/mcmap,WRIM/mcmap,Zahl/mcmap,WRIM/mcmap,WRIM/mcmap,WRIM/mcmap-mirror,WRIM/mcmap-mirror,WRIM/mcmap-mirror,WRIM/mcmap,Zahl/mcmap