Steps to reproduce the issue

• Issue should be fixed before test: #34964
• Current nightly.
• Activate error reporting in Joomla configuration: Maximum
• Go to Menus > Manage.
• Set filter on Administrator to create a backend menu.
• Click button New.
• Enter Title and Unique name.
• Field Import a preset: Select Preset Alternative Main Menu.
• Save & Close
• Put a tick in front of the new menu to activate button Download as Preset and click on button.
• Save XML file.
• Open the exported XML file in an text editor

Expected result

• No PHP warnings.

Actual result

First lines of exported file:

Warning</b>:  Undefined property: Joomla\CMS\Menu\AdministratorMenuItem::$class in /administrator/components/com_menus/src/View/Menu/XmlView.php on line 137

Warning:  Undefined property: Joomla\CMS\Menu\AdministratorMenuItem::$submenu in /administrator/components/com_menus/src/View/Menu/XmlView.php on line 175

Warning:  foreach() argument must be of type array|object, null given in /administrator/components/com_menus/src/View/Menu/XmlView.php on line 175

• PHP 8.0.6 (Linux dd51328 5.4.0-80-generic # 90-Ubuntu SMP Fri Jul 9 22:49:44 UTC 2021 x86_64 )