Default arguments when no register_gen_reset was called

lib/gen_reset.ex

@@ -8,7 +8,11 @@ defmodule GenReset do
   defmacro __using__(_args) do
     quote do
       def handle_call(:"$gen_reset", _from, state) do
-        case init(:erlang.get(:"$gen_reset_initial_args")) do
+        args = case :erlang.get(:"$gen_reset_initial_args") do
+          :undefined -> nil
+          rest -> rest
+        end
+        case init(args) do
           {:ok, state} ->
             {:reply, :ok, state}