requireAuth property Null safety

1. sendbird_sdk
2. command
3. Command
4. requireAuth property

Command class

1. Constructors
2. Command
3. fromJson
4. Properties
5. cmd
6. errorCode
7. errorMessage
8. hasError
9. hashCode
10. isAckRequired
11. isDeletedMessage
12. isDelivery
13. isError
14. isLogin
15. isMemberCountChange
16. isNewMessage
17. isReaction
18. isRead
19. isSessionExpired
20. isSystemEvent
21. isThread
22. isUpdatedMessage
23. isUpdatedPoll
24. isUserEvent
25. isVote
26. payload
27. replyToChannel
28. requestId
29. requireAuth
30. runtimeType
31. timestamp
32. Methods
33. encode
34. noSuchMethod
35. toJson
36. toString
37. Operators
38. operator ==
39. Static methods
40. buildEndTyping
41. buildEnterChannel
42. buildExitChannel
43. buildFileMessage
44. buildLOGIUpdateSessionKey
45. buildMessageMACK
46. buildPing
47. buildRead
48. buildStartTyping
49. buildUpdateFileMessage
50. buildUpdateMessageMetaArray
51. buildUpdateUserMessage
52. buildUserMessage