startMedia method Null safety

1. baguette
2. MediaViewerView
3. MediaViewerView
4. startMedia method

MediaViewerView class

1. Constructors
2. MediaViewerView
3. Properties
4. context
5. hashCode
6. mounted
7. runtimeType
8. widget
9. Methods
10. activate
11. build
12. buildContent
13. deactivate
14. debugFillProperties
15. didChangeAccessibilityFeatures
16. didChangeAppLifecycleState
17. didChangeDependencies
18. didChangeLocales
19. didChangeMetrics
20. didChangePlatformBrightness
21. didChangeTextScaleFactor
22. didHaveMemoryPressure
23. didPopRoute
24. didPushRoute
25. didPushRouteInformation
26. didUpdateWidget
27. dispose
28. getViewModel
29. initState
30. isMediaPlaying
31. isVideo
32. noSuchMethod
33. notifyChanges
34. onCreate
35. onDispose
36. reassemble
37. setState
38. setViewModel
39. startMedia
40. stopMedia
41. toDiagnosticsNode
42. toString
43. toStringShort
44. Operators
45. operator ==