Include child nodes doesn't work if display as label is selected

[brionyfactory73]

Which exact Umbraco version are you using? For example: 8.7.0 - don't just write v8 or v9

13.5.2

Bug summary

If I create a nav item and check both the "Display as label" and "Include children" checkboxes, the children don't get included.

Specifics

The Umbraco back office shows both checkboxes as selected and shows the "Includes child pages" label on the nav item.

When I debug, there are no child nodes included and the "IncludeChildNodes" property is set to false.

Steps to reproduce

1. Add a nav item that is a link item type and select an Umbraco content page that has child items.
2. Check both "Display as label" and "Include children" checkboxes.
3. Debug and check if the UmbNavItem has any children.

Expected result / actual result

I'd expect the nav item to include the children but it doesn't include any. I'd also expect the IncludeChildNodes property to be set to true but it's set to false, despite the checkbox being checked in Umbraco.