implyBack property Null safety

1. baguette
2. ToolBar
3. ToolBar
4. implyBack property

ToolBar class

1. Constructors
2. ToolBar
3. Properties
4. actions
5. hashCode
6. icon
7. implyBack
8. key
9. preferredSize
10. runtimeType
11. title
12. Methods
13. build
14. createElement
15. debugDescribeChildren
16. debugFillProperties
17. noSuchMethod
18. toDiagnosticsNode
19. toString
20. toStringDeep
21. toStringShallow
22. toStringShort
23. Operators
24. operator ==