Fix warning on unused parameter

Change-Id: Iae3dc3327630ecb62de19277a83ea3f372d38ea3
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/plugins/qt4projectmanager/qt-desktop/qt4runconfiguration.cpp

@@ -431,6 +431,7 @@ void Qt4RunConfigurationWidget::termToggled(bool on)
 
 void Qt4RunConfigurationWidget::qvfbToggled(bool on)
 {
+    Q_UNUSED(on);
     m_ignoreChange = true;
     m_ignoreChange = false;
 }