assetPath property Null safety

1. flutter_json_widgets
2. flutter_widget
3. FlutterWidget
4. assetPath property

FlutterWidget class

1. Constructors
2. FlutterWidget
3. asset
4. json
5. network
6. Properties
7. assetPath
8. customWidgets
9. emptyBuilder
10. formData
11. hashCode
12. httpClient
13. json
14. key
15. onLinkTap
16. request
17. runtimeType
18. widget
19. wrappingBuilder
20. Methods
21. createElement
22. createState
23. debugDescribeChildren
24. debugFillProperties
25. noSuchMethod
26. toDiagnosticsNode
27. toString
28. toStringDeep
29. toStringShallow
30. toStringShort
31. Operators
32. operator ==