Navigation Submenu Block: Mark Navigation Submenu parent as invalid when linked page is deleted

[dhruvikpatel18]

Closes #44760

What?

Ensures that when the parent page of a Navigation Submenu block is deleted, it is marked as (Invalid) in the editor, similar to other navigation links.

Why?

Currently, when a Navigation Submenu has a parent item linked to a page, and that page is deleted, the editor does not indicate that the link is invalid. This behavior is inconsistent with other navigation links, which display (Invalid) when their linked page is removed.

This issue affects both Classic and FSE themes, and results in the editor displaying an outdated menu structure, even though the front-end correctly removes the deleted page’s submenu.

Testing Instructions

1. Add a Navigation block to a site.
2. Create a submenu, setting its parent item to link to an existing Page.
3. Publish the content.
4. Delete the parent page from the site.
5. Refresh the editor where the Navigation block is used.
6. Expected Result: The submenu parent item should now display (Invalid) next to its label in the editor.

Screenshots or screencast

Before

Screen.Recording.2025-02-11.at.2.30.00.PM.mov

After

Screen.Recording.2025-02-11.at.2.43.04.PM.mov

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Co-authored-by: dhruvikpatel18 <[email protected]>
Co-authored-by: getdave <[email protected]>
Co-authored-by: cuemarie <[email protected]>

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