[COMPONENT][Notification] Always pre-add Actor subscribers when notifying

components/Notification/Notification.php

@@ -81,6 +81,9 @@ class Notification extends Component
     {
         // Ensure targets are all actor objects and unique
         $effective_targets = [];
+        foreach ($sender->getSubscribers() as $subscriber) {
+            $effective_targets[$subscriber->getId()] = $subscriber;
+        }
         foreach ($targets as $target) {
             if (\is_int($target)) {
                 $target_id     = $target;