message: Fix Event unsubscribe
diff: @@ -196,6 +196,7 @@ export default class Event<Param, Ret = void> {
  // If this callback was the root subscription, then set it to the next one
  if (callback === this.rootSubscription) {
  this.rootSubscription = Array.from(this.subscriptions)[0];
  + this.subscriptions.delete(this.rootSubscription);
  this.onSubscriptionChange();
  return;
  }
  