[ch09] - ProcessRegistry restarts crash the App

[ajayvigneshk]

In Chapter 09, section 9.1, the following code on iex

Todo.System.start_link
Process.exit(Process.whereis(Todo.ProcessRegistry),:kill)

causes the Supervisor to crash(after trying to restart the children). Trying to inspect the result of Registry.start_link, it shows

{:error,
 {:shutdown,
  {:failed_to_start_child, Todo.ProcessRegistry.PIDPartition0,
   {:already_started, #PID<0.183.0>}}}}

Am guessing that this happens because the supervisor is starting ProcessRegistry in succession before the actual Registry is shutdown and keeps erroring 3 times, ending up in shutdown.
Is that correct?
How to handle this scenario gracefully?