Don't adapt to the new screen if it's null

shell/desktopview.cpp

@@ -91,6 +91,9 @@ void DesktopView::moveEvent(QMoveEvent* ev)
 
 void DesktopView::adaptToScreen()
 {
+    //This happens sometimes, when shutting down the process
+    if (!screen())
+        return;
     qDebug() << "adapting to screen" << screen()->name() << this;
     if (m_fillScreen) {
         setGeometry(screen()->geometry());
@@ -105,6 +108,9 @@ void DesktopView::adaptToScreen()
 
 void DesktopView::ensureStayBehind()
 {
+    //This happens sometimes, when shutting down the process
+    if (!screen())
+        return;
     if (m_stayBehind) {
         KWindowSystem::setType(winId(), NET::Desktop);
     } else {

shell/panelview.cpp

@@ -103,6 +103,8 @@ PanelView::PanelView(Plasma::Containment *cont, QWindow *parent)
     //When the screen is set, the screen is recreated internally, so we need to
     //set anything that depends on the winId()
     connect(this, &QWindow::screenChanged, this, [=]() {
+            if (!screen())
+                return;
             KWindowSystem::setType(winId(), NET::Dock);
             setVisibilityMode(m_visibilityMode);
             showTemporarily();