selectedIcon property Null safety

1. flutter_json_widgets
2. widget
3. IconButton
4. selectedIcon property

IconButton class

1. Constructors
2. IconButton
3. fromJson
4. Properties
5. alignment
6. autofocus
7. color
8. constraints
9. copyWith
10. disabledColor
11. enableFeedback
12. focusColor
13. hashCode
14. highlightColor
15. hoverColor
16. icon
17. iconSize
18. isSelected
19. key
20. mouseCursor
21. onPressed
22. padding
23. runtimeType
24. selectedIcon
25. splashColor
26. splashRadius
27. tooltip
28. visualDensity
29. Methods
30. map
31. mapOrNull
32. maybeMap
33. maybeWhen
34. noSuchMethod
35. toJson
36. toString
37. when
38. whenOrNull
39. Operators
40. operator ==