mcl_attached: Check if dir is nil

mods/CORE/mcl_attached/init.lua

@@ -7,6 +7,7 @@ minetest.check_single_for_falling = function(pos)
 	local node = minetest.get_node(pos)
 	if minetest.get_item_group(node.name, "attached_node_facedir") ~= 0 then
 		local dir = minetest.facedir_to_dir(node.param2)
+		if dir then
 			local cpos = vector.add(pos, dir)
 			local cnode = minetest.get_node(cpos)
 			if minetest.get_item_group(cnode.name, "solid") == 0 then
@@ -18,6 +19,7 @@ minetest.check_single_for_falling = function(pos)
 				ret = true
 			end
 		end
+	end
 
 	return ret_o or ret
 end