deleting from database

In documentation of `Hive` we have `delete` method for deleting something from database, but this method don't delete from database and it only do `null` on index of found data and it cause some problem when we want to listen to database changes or making `ListView` with `null` data,

another problem is `.values` that return `non-nullable` data and when we try to make a `ListView` we get `null` error