NERoomChatFileMessage constructor Null safety

1. netease_roomkit
2. netease_roomkit
3. NERoomChatFileMessage
4. NERoomChatFileMessage constructor

NERoomChatFileMessage class

1. Constructors
2. NERoomChatFileMessage
3. Properties
4. displayName
5. extension
6. fromNick
7. fromUserUuid
8. hashCode
9. md5
10. message
11. messageType
12. messageUuid
13. of
14. path
15. runtimeType
16. size
17. thumbPath
18. time
19. toUserUuidList
20. url
21. Methods
22. noSuchMethod
23. toString
24. Operators
25. operator *
26. operator ==