Fixed the assertion in QxtStringSpinBox::textFromValue().
Fixed the assertion in QxtStringSpinBox::textFromValue().

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