LDErrorKind constructor Null safety

1. launchdarkly_flutter_client_sdk
2. launchdarkly_flutter_client_sdk
3. LDErrorKind
4. LDErrorKind const constructor

LDErrorKind enum

1. Constructors
2. LDErrorKind
3. Values
4. CLIENT_NOT_READY
5. FLAG_NOT_FOUND
6. MALFORMED_FLAG
7. USER_NOT_SPECIFIED
8. WRONG_TYPE
9. EXCEPTION
10. UNKNOWN
11. Properties
12. hashCode
13. index
14. runtimeType
15. Methods
16. noSuchMethod
17. toString
18. Operators
19. operator ==
20. Constants
21. values