appDisplay: Clear animateLater callbacks when unmapping

In some situations we could end up not with lingering 'view-loaded'
handler. This could result in delayed spring animate-in being initiated,
e.g. after a minute after the activities overview was already closed.

Fix this by removing any lingering signal or later handlers when
unmapping.

Fixes: 5c33fe4a0a4eb4ed

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1155

js/ui/appDisplay.js

@@ -291,6 +291,11 @@ var BaseAppView = GObject.registerClass({
         }
     }
 
+    vfunc_unmap() {
+        this._clearAnimateLater();
+        super.vfunc_unmap();
+    }
+
     animateSwitch(animationDirection) {
         this.remove_all_transitions();
         this._grid.remove_all_transitions();