Fix build failed

debian/control

@@ -9,6 +9,7 @@ Build-Depends: cmake,
                libkf5windowsystem-dev,
                libqt5xdg-dev,
                libdbusmenu-qt5-dev,
+               libxcb-shape0-dev,
                libxcb1-dev,
                libxcb-ewmh-dev,
                qtbase5-dev,

widgetstyle/blurhelper.cpp

@@ -41,6 +41,7 @@
 #include <QVariant>
 #include <QEvent>
 #include <QPainterPath>
+#include <QApplication>
 #include <QX11Info>
 
 // XCB
@@ -129,7 +130,7 @@ void BlurHelper::enableBlurBehind(QWidget *widget, bool enable, qreal windowRadi
         return;
 
     if (enable) {
-        qreal devicePixelRatio = widget->screen()->devicePixelRatio();
+        qreal devicePixelRatio = qApp->devicePixelRatio();
         QPainterPath path;
         path.addRoundedRect(QRectF(QPoint(0, 0), widget->size() * devicePixelRatio),
                             windowRadius * devicePixelRatio,