DatabaseUtils constructor Null safety

1. fact_browser
2. database_utils
3. DatabaseUtils
4. DatabaseUtils constructor

DatabaseUtils class

1. Constructors
2. DatabaseUtils
3. Properties
4. hashCode
5. runtimeType
6. safeStorage
7. Methods
8. checkToken
9. getStatement
10. login
11. logout
12. noSuchMethod
13. searchStatements
14. sendData
15. toString
16. updateData
17. Operators
18. operator ==