terraria service: fixup worldPath option type

Otherwise, using the defaults results in a type error.

Changed files
+1 -1
nixos
modules
services
games
+1 -1
nixos/modules/services/games/terraria.nix
···
};
worldPath = mkOption {
-
type = types.path;
+
type = types.nullOr types.path;
default = null;
description = ''
The path to the world file (<literal>.wld</literal>) which should be loaded.