toggleMute static method Null safety

1. baguette
2. MediaVolume
3. MediaVolume
4. toggleMute static method

MediaVolume class

1. Constructors
2. MediaVolume
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Static methods
12. getMaxVolume
13. getMinVolume
14. getVolume
15. isMute
16. setMute
17. toggleMute