removeColumn + mapper = QSqlQuery::value not positioned..

If I set up a QSqlRelationalTableModel, with 1+ relation, and remove a column[1] and use a QDataWidgetMapper [2] to map data from the model to a custom widget, ifand after call mapper->submit() [3] , I see on console the message

QSqlQuery::value: not positioned on a valid record

and the model isn't updated.

[1] mainwindow.cpp:51
[2] editingtablemask.cpp:14
[3] editingtablemask.cpp:77

I tested this example program on OS X and Linux x64_86, and get the same result (model isn't updated)
I post also on Qt-interest mailing list, this is the link

http://lists.trolltech.com/pipermail/qt-interest/2010-February/019439.html