fix #292,workaround for KF5.32 empty mask

--in KF5.32 FrameSvg returns many times a mask
that is an empty QRegion(). this patch makes
sure that at least our rectangular metrics
for masks and effectsarea are used instead.
Of course this means that themes with rounded
corners dont look as they should in !compositing
state

app/dockview.cpp

@@ -899,7 +899,13 @@ void DockView::setMaskArea(QRect area)
         m_background->setEnabledBorders(enabledBorders());
         m_background->resizeFrame(area.size());
         QRegion fixedMask = m_background->mask();
-        fixedMask.translate(area.x(), area.y());
+        fixedMask.translate(m_maskArea.x(), m_maskArea.y());
+
+        //! fix for KF5.32 that return empty QRegion's for the mask
+        if (fixedMask.isEmpty()) {
+            fixedMask = QRegion(m_maskArea);
+        }
+
         setMask(fixedMask);
     }
 
@@ -977,6 +983,11 @@ void DockView::updateEffects()
             QRegion fixedMask = m_background->mask();
             fixedMask.translate(m_effectsArea.x(), m_effectsArea.y());
 
+            //! fix for KF5.32 that return empty QRegion's for the mask
+            if (fixedMask.isEmpty()) {
+                fixedMask = QRegion(m_effectsArea);
+            }
+
             KWindowEffects::enableBlurBehind(winId(), true, fixedMask);
             KWindowEffects::enableBackgroundContrast(winId(), m_theme.backgroundContrastEnabled(),
                     m_theme.backgroundContrast(),