code: void invokeSubscriber(PendingPost pendingPost) {
          Object event = pendingPost.event;
          Subscription subscription = pendingPost.subscription;
          PendingPost.releasePendingPost(pendingPost);
          if (subscription.active) {
              invokeSubscriber(subscription, event);
          }
      }
docs: Invokes the subscriber if the subscriptions is still active. Skipping subscriptions prevents race conditions
  between {@link #unregister(Object)} and event delivery. Otherwise the event might be delivered after the
  subscriber unregistered. This is particularly important for main thread delivery and registrations bound to the
  live cycle of an Activity or Fragment.