preserve 'flat' property of QxtGroupBox when expanding refs #1
preserve 'flat' property of QxtGroupBox when expanding
refs #1

hrobeers/qxtweb-qt5,mmitkevich/libqxt,hrobeers/qxtweb-qt5,mmitkevich/libqxt,mmitkevich/libqxt,hrobeers/qxtweb-qt5,hrobeers/qxtweb-qt5,hrobeers/qxtweb-qt5,mmitkevich/libqxt