Unify Window::killWindow() for unmanaged windows

src/killwindow.cpp

@@ -32,15 +32,10 @@ void KillWindow::start()
     OSD::show(i18n("Select window to force close with left click or enter.\nEscape or right click to cancel."),
               QStringLiteral("window-close"));
     kwinApp()->startInteractiveWindowSelection(
-        [](KWin::Window *t) {
+        [](KWin::Window *window) {
             OSD::hide();
-            if (!t) {
-                return;
-            }
-            if (Window *c = static_cast<Window *>(t->isClient() ? t : nullptr)) {
-                c->killWindow();
-            } else if (Unmanaged *u = qobject_cast<Unmanaged *>(t)) {
-                xcb_kill_client(kwinApp()->x11Connection(), u->window());
+            if (window) {
+                window->killWindow();
             }
         },
         QByteArrayLiteral("pirate"));

src/unmanaged.cpp

@@ -235,4 +235,9 @@ void Unmanaged::damageNotifyEvent()
     }
 }
 
+void Unmanaged::killWindow()
+{
+    xcb_kill_client(kwinApp()->x11Connection(), window());
+}
+
 } // namespace

src/unmanaged.h

@@ -46,7 +46,7 @@ public:
     bool isMovableAcrossScreens() const override { return false; }
     bool takeFocus() override { return false; }
     bool wantsInput() const override { return false; }
-    void killWindow() override { /* nothing to do */ }
+    void killWindow() override;
     void destroyWindow() override { /* nothing to do */ }
     void closeWindow() override { /* nothing to do */ }
     bool acceptsFocus() const override { return false; }