closeDialog: Make dialog inactive while fading out

Otherwise the user might click Kill, which would crash if the fade-out
was triggered because a Wayland window was closed.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/1032


(cherry picked from commit 32fa060a62)

js/ui/closeDialog.js

@@ -192,6 +192,7 @@ var CloseDialog = GObject.registerClass({
         this._dialog = null;
         this._removeWindowEffect();
 
+        dialog.makeInactive();
         dialog._dialog.ease({
             scale_y: 0,
             mode: Clutter.AnimationMode.LINEAR,

js/ui/dialog.js

@@ -51,10 +51,16 @@ class Dialog extends St.Widget {
                            y_align: St.Align.START });
     }
 
-    _onDestroy() {
+    makeInactive() {
         if (this._eventId != 0)
             this._parentActor.disconnect(this._eventId);
         this._eventId = 0;
+
+        this.buttonLayout.get_children().forEach(c => c.set_reactive(false));
+    }
+
+    _onDestroy() {
+        this.makeInactive();
     }
 
     _modalEventHandler(actor, event) {