[lrfurn] Fix global variable. Fix #508

- Us: "But it's okay in Lua to use undefined variables!"
 - Minetest: "Yep. But we don't want that. Now cooperate."

mods/homedecor_modpack/lrfurn/coffeetable.lua

@@ -29,7 +29,7 @@ minetest.register_node("lrfurn:coffeetable_back", {
 		local node = minetest.get_node(pos)
 		local param2 = node.param2
 
-		if lrfurn.check_forward(pos, fdir, false, placer) then
+		if lrfurn.check_forward(pos, nil, false, placer) then
 
 			node.name = "lrfurn:coffeetable_front"
 			if param2 == 0 then