onChangeTab method Null safety

1. baguette
2. TabsScreen
3. TabsScreen<T extends TabsScreenWidget>
4. onChangeTab method

TabsScreen class

1. Constructors
2. TabsScreen
3. Properties
4. context
5. hashCode
6. mounted
7. runtimeType
8. widget
9. Methods
10. activate
11. alignTabs
12. build
13. buildContent
14. buildDrawer
15. buildNavigationBar
16. buildTabs
17. buildTabsContent
18. buildToolBar
19. countTabs
20. createTicker
21. deactivate
22. debugFillProperties
23. didChangeAccessibilityFeatures
24. didChangeAppLifecycleState
25. didChangeDependencies
26. didChangeLocales
27. didChangeMetrics
28. didChangePlatformBrightness
29. didChangeTextScaleFactor
30. didHaveMemoryPressure
31. didPop
32. didPopNext
33. didPopRoute
34. didPush
35. didPushNext
36. didPushRoute
37. didPushRouteInformation
38. didUpdateWidget
39. dispose
40. getTabIndex
41. getViewModel
42. initialTab
43. initState
44. isShowActivity
45. noSuchMethod
46. notifyChanges
47. onChangeTab
48. onCreate
49. onDispose
50. onPause
51. onResume
52. onStart
53. onStop
54. openTab
55. reassemble
56. setState
57. setViewModel
58. showActivity
59. toDiagnosticsNode
60. toString
61. toStringShort
62. Operators
63. operator ==