RTCRoomStats.empty constructor Null safety

1. volc_engine_rtc
2. bytertc_common_defines
3. RTCRoomStats
4. RTCRoomStats.empty constructor

RTCRoomStats class

1. Constructors
2. RTCRoomStats
3. empty
4. fromMap
5. Properties
6. duration
7. hashCode
8. rtt
9. runtimeType
10. rxAudioKBitrate
11. rxBytes
12. rxCellularKBitrate
13. rxJitter
14. rxKBitrate
15. rxLostrate
16. rxScreenKBitrate
17. rxVideoKBitrate
18. txAudioKBitrate
19. txBytes
20. txCellularKBitrate
21. txJitter
22. txKBitrate
23. txLostrate
24. txScreenKBitrate
25. txVideoKBitrate
26. userCount
27. Methods
28. noSuchMethod
29. toString
30. Operators
31. operator ==