NotificationQueueService constructor Null safety

1. irte_engine
2. notification_queue_service
3. NotificationQueueService
4. NotificationQueueService constructor

NotificationQueueService class

1. Constructors
2. NotificationQueueService
3. Properties
4. hashCode
5. hasListeners
6. initialized
7. isClosed
8. listeners
9. onDelete
10. onStart
11. runtimeType
12. Methods
13. $configureLifeCycle
14. addListener
15. addListenerId
16. addNotification
17. dispose
18. disposeId
19. noSuchMethod
20. notifyChildrens
21. onClose
22. onInit
23. onReady
24. processQueue
25. refresh
26. refreshGroup
27. removeListener
28. removeListenerId
29. toString
30. update
31. Operators
32. operator ==