UnknownError constructor Null safety

1. sendbird_sdk
2. error
3. UnknownError
4. UnknownError constructor

UnknownError class

1. Constructors
2. UnknownError
3. Properties
4. code
5. hashCode
6. message
7. runtimeType
8. stackTrace
9. Methods
10. byaction
11. noSuchMethod
12. toJson
13. toString
14. Operators
15. operator ==