QDataWidgetMapper not submitting data with QSqlRelationalTableModel

This problem might be related to Qt QTBUG-16299.

The Qdatawidgetmapper combobox does not submit data to the database field. The combobox displays data from another table references using an id. But the selected id is not stored in the database.

The database used in the example code is a sqlite database which is opened in initdb.h. Change the databasename to your own database. It creates the
tables drivers and cars and inserts a couple of records.

The mainwindow shows data from the cars table and the combobox shows the drivers lastname from the drivers table.
You can select another driver in the combobox but this data is not stored.
You can add a record in the cars table, but the drivers_id is left empty in the new record and the new record will not be showed in the form, although it does exist in the table.