"Blocked attempt to show a 'beforeunload' confirmation panel" when navigating away from MenuPart editor

Describe the bug

To Reproduce

This is vague and needs more investigation since I see the actual browser log entry only during UI tests (here). Thus I don’t have a solid repro, but the issue does come up reliably if you run that test. So, supposedly:

1. Navigate to a MenuPart editor, e.g. the editor of Main Menu when you’ve set up the site with the blog recipe.
2. Don’t do anything (?) or perhaps only edit the Title (but not the menu items, don’t change their order, for example).
3. Do anything that causes you to navigate away.
4. Note a browser console entry similar to this one in Chrome:

3/21/2022 7:49:13 PM UTC | Severe | intervention | https://localhost:9024/Admin/Contents/ContentItems/4nqq58rc9skbf6pdnmhzn3mmx7/Edit?admin=-1181914940 - Blocked attempt to show a 'beforeunload' confirmation panel for a frame that never had a user gesture since its load. https://www.chromestatus.com/feature/5082396709879808

This is because of the window.onbeforeunload code in MenuPart.Edit.cshtml (though it ought to not display a dialog unless the menu items’ order is changed). See the linked https://chromestatus.com/feature/5082396709879808 and https://developer.mozilla.org/en-US/docs/Web/API/BeforeUnloadEvent.

Note that TaxonomyPart.Edit.cshtml has the same issue.

Expected behavior

No console log entry.