Fix crash with LBM

init.lua

@@ -659,6 +659,10 @@ minetest.register_lbm({
 			color = ""
 		end
 
+		if color == "_black" or color == "_white" or color == "_dark_grey" then
+			color = "_grey"
+		end
+
 		minetest.set_node(pos, { name = "unifiedbricks:"..class.."stonebrick"..color..shape, param2 = paletteidx+old_param2 })
 	end
 })