renderFrameRate property Null safety

1. nertc
2. nertc
3. NERtcVideoLayerSendStats
4. renderFrameRate property

NERtcVideoLayerSendStats class

1. Constructors
2. fromMap
3. Properties
4. captureFrameRate
5. encoderBitrate
6. encoderName
7. encoderOutputFrameRate
8. hashCode
9. height
10. layerType
11. renderFrameRate
12. runtimeType
13. sendBitrate
14. sentFrameRate
15. targetBitrate
16. width
17. Methods
18. noSuchMethod
19. toString
20. Operators
21. operator ==