onRate property Null safety

1. baguette
2. RateWidget
3. RateWidget
4. onRate property

RateWidget class

1. Constructors
2. RateWidget
3. Properties
4. hashCode
5. height
6. key
7. margin
8. maxRate
9. onRate
10. padding
11. rate
12. runtimeType
13. visibility
14. width
15. Methods
16. createElement
17. createState
18. debugDescribeChildren
19. debugFillProperties
20. noSuchMethod
21. toDiagnosticsNode
22. toString
23. toStringDeep
24. toStringShallow
25. toStringShort
26. Operators
27. operator ==