setAccount method Null safety

1. baguette
2. AccountManager
3. AccountManager
4. setAccount method

AccountManager class

1. Constructors
2. AccountManager
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. addPlugin
8. cleanPlugins
9. getAccount
10. getPlugin
11. noSuchMethod
12. removePlugin
13. setAccount
14. toString
15. Operators
16. operator ==