Fix build without features.groupbox

Change-Id: Ic040d0ba69620cf49700d83e45ccd9b8c363e587
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/widgets/styles/qfusionstyle.cpp

@@ -465,6 +465,7 @@ void QFusionStyle::drawPrimitive(PrimitiveElement elem,
 
     switch (elem) {
 
+#if QT_CONFIG(groupbox)
     // No frame drawn
     case PE_FrameGroupBox:
     {
@@ -481,6 +482,7 @@ void QFusionStyle::drawPrimitive(PrimitiveElement elem,
         qDrawBorderPixmap(painter, frame, QMargins(6, 6, 6, 6), pixmap);
         break;
     }
+#endif // QT_CONFIG(groupbox)
     case PE_IndicatorBranch: {
         if (!(option->state & State_Children))
             break;