Minor renames of parameters of non-user API an some code cleanup

akka-actor/src/main/scala/akka/dispatch/MessageHandling.scala

@@ -22,13 +22,8 @@ final case class MessageInvocation(receiver: ActorRef,
                                    senderFuture: Option[Promise[Any]]) {
   if (receiver eq null) throw new IllegalArgumentException("Receiver can't be null")
 
-  def invoke() {
-    try {
-      receiver.invoke(this)
-    } catch {
-      case e: NullPointerException ⇒ throw new ActorInitializationException(
-        "Don't call 'self ! message' in the Actor's constructor (in Scala this means in the body of the class).")
-    }
+  final def invoke() {
+    receiver invoke this
   }
 }
 
@@ -177,7 +172,7 @@ trait MessageDispatcher {
       val uuid = i.next()
       Actor.registry.local.actorFor(uuid) match {
         case Some(actor) ⇒ actor.stop()
-        case None        ⇒ {}
+        case None        ⇒
       }
     }
   }