width property Null safety

1. jrpn
2. view.back_panel
3. BPItem
4. width abstract property

BPItem class

1. Constructors
2. BPItem
3. Properties
4. align
5. hashCode
6. runtimeType
7. width
8. Methods
9. noSuchMethod
10. paint
11. toString
12. Operators
13. operator ==