archive property Null safety

1. baguette
2. Conversation
3. Conversation
4. archive property

Conversation class

1. Constructors
2. Conversation
3. Properties
4. archive
5. conversationID
6. date
7. hashCode
8. hints
9. icon
10. me
11. members
12. message
13. runtimeType
14. title
15. Methods
16. noSuchMethod
17. toString
18. Operators
19. operator ==