doctor property Null safety

1. farmershands
2. chat_list_subscreen
3. ChatListSubScreen
4. doctor property

ChatListSubScreen class

1. Constructors
2. ChatListSubScreen
3. Properties
4. doctor
5. hashCode
6. key
7. runtimeType
8. title
9. Methods
10. createElement
11. createState
12. debugDescribeChildren
13. debugFillProperties
14. noSuchMethod
15. toDiagnosticsNode
16. toString
17. toStringDeep
18. toStringShallow
19. toStringShort
20. Operators
21. operator ==
22. Constants
23. routeName