QDataWidgetMapper::toPrevious() may not work when model is QSql(Relational)TableModel

QDataWidgetMapper::toPrevious() does not work if the model is QSqlTableModel, or the model is QSqlRelationalTableModel and the item delegate is QSqlRelationalDelegate, and the model's edit strategy is OnFieldChange or OnRowChange.

This is reproducible with the SQL Widget Mapper example by commenting out the setEditStrategy() call in setupModel().

It is also reproducible by modifying the example to use a QSqlTableModel instead of a QSqlRelationalModel, using the data widget mapper's default item delegate and setting the edit strategy to OnFieldChange or OnRowChange.