keyboard: Bind emoji pager visibility to swipeTracker enabled state

The swipeTracker may connect gestures on the stage, so we might end up
in the odd situation that the swipeTracker is handling events for an
invisible actor. Avoid doing this.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2543>

js/ui/keyboard.js

@@ -687,6 +687,10 @@ var EmojiPager = GObject.registerClass({
         this._swipeTracker = swipeTracker;
 
         this.connect('destroy', () => this._onDestroy());
+
+        this.bind_property(
+            'visible', this._swipeTracker, 'enabled',
+            GObject.BindingFlags.DEFAULT);
     }
 
     _onDestroy() {