Fix drawing of styled frames for QQuickItems

There is a special case for comboboxes when drawing a styled frame, but for
some reason it didn't actually check whether the QQuickItem is a combobox,
there was only a comment...

This adds the check, which means that QQuickItems get a proper frame now
instead of a combobox popup.

kstyle/breezestyle.cpp

@@ -5424,7 +5424,8 @@ namespace Breeze
             case QFrame::StyledPanel:
             {
 
-                if( isQtQuickControl( option, widget ) )
+                if( isQtQuickControl( option, widget )
+                    && option->styleObject->property( "elementType" ).toString() == QLatin1String( "combobox" ) )
                 {
 
                     // ComboBox popup frame