[5.2] Admin menu recovery mode

[brianteeman]

Steps to reproduce the issue

Create a new admin menu. Either use a preset or add a menu item to it.
Publish this new admin menu in a module in position menu
After the message to turn on the menu recovery mode is displayed make sure you click on it to enable recovery mode

Expected result

no errors

Actual result

you might need to navigate to another page but a series of errors are displayed such as

Warning: Undefined property: Joomla\CMS\Menu\AdministratorMenuItem::$element in /home/public_html/administrator/modules/mod_menu/src/Menu/CssMenu.php on line 319

Warning: Undefined property: Joomla\CMS\Menu\AdministratorMenuItem::$class in /home/public_html/administrator/modules/mod_menu/src/Menu/CssMenu.php on line 495

System information (as much as possible)

Additional comments

[chmst]

Closing as there is a PR. Please test #44318