fix crash from ghostedge in X11

--when unloading a layout under X11
when MultipleLayouts are used sometimes
a crash was occuring.

app/dock/screenedgeghostwindow.cpp

@@ -62,15 +62,16 @@ ScreenEdgeGhostWindow::ScreenEdgeGhostWindow(DockView *view) :
         connect(this, &QWindow::visibleChanged, this, [&]() {
             //! IMPORTANT!!! ::: This fixes a bug when closing an Activity all docks from all Activities are
             //!  disappearing! With this they reappear!!!
+            if (m_dockView && m_dockView->managedLayout()) {
                 if (!isVisible()) {
                     QTimer::singleShot(100, [this]() {
-                    if (!m_inDelete && !isVisible()) {
+                        if (!m_inDelete && !isVisible() && m_dockView && m_dockView->managedLayout()) {
                             setVisible(true);
                         }
                     });
 
                     QTimer::singleShot(1500, [this]() {
-                    if (!m_inDelete && !isVisible()) {
+                        if (!m_inDelete && !isVisible() && m_dockView && m_dockView->managedLayout()) {
                             setVisible(true);
                         }
                     });
@@ -83,6 +84,7 @@ ScreenEdgeGhostWindow::ScreenEdgeGhostWindow(DockView *view) :
                         KWindowSystem::setOnAllDesktops(winId(), true);
                     }
                 }
+            }
         });
     }