Revert "Revert "modalDialog: Destroy dialogs on close""

This reverts commit 007820b7c1.

(I only meant to revert that in my local branch)

js/ui/endSessionDialog.js

@@ -225,7 +225,8 @@ const EndSessionDialog = new Lang.Class({
     Extends: ModalDialog.ModalDialog,
 
     _init: function() {
-        this.parent({ styleClass: 'end-session-dialog' });
+        this.parent({ styleClass: 'end-session-dialog',
+                      destroyOnClose: false });
 
         this._user = AccountsService.UserManager.get_default().get_user(GLib.get_user_name());