uic: QToolBox doesn't include <QtGui/QLayout> but uses QLayout when you set tabSpacing field (and perhaps others) on unlaidout forms

This bug appears in QCreator when you set (for exemple) tabSpacing field of a QToolBox. Indeed, the generated file ui_myWidget.h try to set the value but can't.

In ui_myWidget.h:
the line "toolBox->layout()->setSpacing(1);" generates this error : ui_myWidget.h:144: erreur : invalid use of incomplete type 'struct QLayout'

And if you add "#include <QtGui/QLayout>" manually, that works but if now you modify again a propertie of the widget, the file is generate again and you need to re-add the include line...