After leaving the Chat you cannot join again

[multimike77]

Reproduction steps:
http://localhost:8080/join/Michael
http://localhost:8080/leave/Michael
http://localhost:8080/join/Michael

Error message showing up in the console:
akka.actor.InvalidActorNameException: actor name [httpClient-Michael] is not unique!
at akka.actor.dungeon.ChildrenContainer$NormalChildrenContainer.reserve(ChildrenContainer.scala:130)
at akka.actor.dungeon.Children$class.reserveChild(Children.scala:76)
at akka.actor.ActorCell.reserveChild(ActorCell.scala:369)
at akka.actor.dungeon.Children$class.makeChild(Children.scala:201)
at akka.actor.dungeon.Children$class.attachChild(Children.scala:41)
at akka.actor.ActorCell.attachChild(ActorCell.scala:369)
at akka.actor.ActorSystemImpl.actorOf(ActorSystem.scala:553)
at org.sandbox.chat.http.Participants$class.createParticipant(Participants.scala:38)
at org.sandbox.chat.http.HttpChatServiceActionsImpl.createParticipant(HttpChatServiceActionsImpl.scala:18)
...