NIMAuthStatus constructor Null safety

1. nim_core
2. nim_core
3. NIMAuthStatus
4. NIMAuthStatus const constructor

NIMAuthStatus enum

1. Constructors
2. NIMAuthStatus
3. Values
4. unknown
5. unLogin
6. connecting
7. logging
8. loggedIn
9. forbidden
10. netBroken
11. versionError
12. pwdError
13. kickOut
14. kickOutByOtherClient
15. dataSyncStart
16. dataSyncFinish
17. Properties
18. hashCode
19. index
20. runtimeType
21. Methods
22. noSuchMethod
23. toString
24. Operators
25. operator ==
26. Constants
27. values