ChatThreadManagerListener constructor Null safety

1. agora_chat_sdk
2. agora_chat_sdk
3. ChatThreadManagerListener
4. ChatThreadManagerListener constructor

ChatThreadManagerListener class

1. Constructors
2. ChatThreadManagerListener
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. onChatThreadCreate
9. onChatThreadDestroy
10. onChatThreadUpdate
11. onUserKickOutOfChatThread
12. toString
13. Operators
14. operator ==