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. messageType
11. messageUuid
12. path
13. runtimeType
14. size
15. thumbPath
16. time
17. toUserUuidList
18. url
19. Methods
20. noSuchMethod
21. toString
22. Operators
23. operator ==