fix: add guard checks when destroying window

src/manager/event_manager.ts

@@ -150,25 +150,37 @@ function applyEffectTo(actor: RoundedWindowActor) {
     // that? I have no idea. But without that, weird bugs can happen. For
     // example, when using Dash to Dock, all opened windows will be invisible
     // *unless they are pinned in the dock*. So yeah, GNOME is magic.
-    connect(actor, 'notify::size', () => handlers.onSizeChanged(actor));
+    connect(actor, 'notify::size', () => {
+        if (actor.metaWindow) {
+             handlers.onSizeChanged(actor);
+        }
+    });
     connect(texture, 'size-changed', () => {
-        handlers.onSizeChanged(actor);
+        if (actor.metaWindow) {
+            handlers.onSizeChanged(actor);
+        }
     });
 
     // Get notified about fullscreen explicitly, since a window must not change in
     // size to go fullscreen
-    connect(actor.metaWindow, 'notify::fullscreen', () =>
-        handlers.onSizeChanged(actor),
-    );
+    connect(actor.metaWindow, 'notify::fullscreen', () => {
+        if (actor.metaWindow) {
+            handlers.onSizeChanged(actor);
+        }
+    });
 
     // Window focus changed.
-    connect(actor.metaWindow, 'notify::appears-focused', () =>
-        handlers.onFocusChanged(actor),
-    );
+    connect(actor.metaWindow, 'notify::appears-focused', () => {
+        if (actor.metaWindow) {
+            handlers.onFocusChanged(actor);
+        }
+    });
 
     // Workspace or monitor of the window changed.
     connect(actor.metaWindow, 'workspace-changed', () => {
-        handlers.onFocusChanged(actor);
+        if (actor.metaWindow) {
+            handlers.onFocusChanged(actor);
+        }
     });
 
     handlers.onAddEffect(actor);