TYPO3 Core

We have a project setup in a way, that an editor can maintain the main menu via a group select (field name is 'tx_site_navigation') in the page properties.

There is a hidden page added in the group select. In TYPO3 10 the MenuProcessor result didn't contain anything for the hidden page.
After upgrading to TYPO3 11 the MenuProcessor seems to try to process the hidden page in some sort of way, resulting in a broken menu in the frontend.

Menu Processor Configuration:

5 = TYPO3\CMS\Frontend\DataProcessing\MenuProcessor
5 {
  if.isTrue.data = levelfield:-1,tx_site_navigation,slide
  cache_period = 604800
  expandAll = 1
  includeSpacer = 0
  levels = 3
  special = list
  special.value = TEXT
  special.value.data = levelfield:-1,tx_site_navigation,slide
  titleField = nav_title // title
}

See attachments for an image of the processed result for the hidden page. 'children' contains all subpages of the root page.

The easy workaround is to remove the hidden page from the group select, but that might not be very intuitive for editors.