cowState property Null safety

1. farmershands
2. report_screen
3. ReportScreenState
4. cowState property

ReportScreenState class

1. Constructors
2. ReportScreenState
3. Properties
4. context
5. cowGroupState
6. cowState
7. hashCode
8. mounted
9. reportState
10. runtimeType
11. vm
12. widget
13. Methods
14. activate
15. build
16. createTicker
17. deactivate
18. debugFillProperties
19. didChangeDependencies
20. didUpdateWidget
21. dispose
22. forceRender
23. initState
24. noSuchMethod
25. reassemble
26. setState
27. toDiagnosticsNode
28. toString
29. toStringShort
30. Operators
31. operator ==