wayland: Use correct signal to get notified when to destroy InputPanelV1Window

The window should be destroyed when the associated surface role is about
to be destroyed. QObject::destroyed is too late.

src/inputpanelv1window.cpp

@@ -39,7 +39,7 @@ InputPanelV1Window::InputPanelV1Window(InputPanelSurfaceV1Interface *panelSurfac
 
     connect(panelSurface, &InputPanelSurfaceV1Interface::topLevel, this, &InputPanelV1Window::showTopLevel);
     connect(panelSurface, &InputPanelSurfaceV1Interface::overlayPanel, this, &InputPanelV1Window::showOverlayPanel);
-    connect(panelSurface, &InputPanelSurfaceV1Interface::destroyed, this, &InputPanelV1Window::destroyWindow);
+    connect(panelSurface, &InputPanelSurfaceV1Interface::aboutToBeDestroyed, this, &InputPanelV1Window::destroyWindow);
 
     connect(workspace(), &Workspace::outputsChanged, this, &InputPanelV1Window::reposition);
 

src/wayland/inputmethod_v1_interface.cpp

@@ -347,6 +347,7 @@ InputPanelSurfaceV1Interface::InputPanelSurfaceV1Interface(SurfaceInterface *sur
 
 InputPanelSurfaceV1Interface::~InputPanelSurfaceV1Interface()
 {
+    Q_EMIT aboutToBeDestroyed();
 }
 
 class InputPanelV1InterfacePrivate : public QtWaylandServer::zwp_input_panel_v1

src/wayland/inputmethod_v1_interface.h

@@ -139,6 +139,7 @@ public:
 Q_SIGNALS:
     void topLevel(OutputInterface *output, Position position);
     void overlayPanel();
+    void aboutToBeDestroyed();
 
 private:
     InputPanelSurfaceV1Interface(SurfaceInterface *surface, quint32 id, QObject *parent);