Alert with message "Delete the alias first," does not work properly in some cases

[stpaultim]

Description of the bug

If trying to put a node alias in the node path, when creating a new layout, one get's a red alert saying that to do this one must first delete the alias with a link to delete the alias.

But, if one clicks on the link and confirms, one get's a white screen of death.

While I recognize that in this case the user is trying to do something that they should not (I think). The results should not be this harsh. We should not provide the option to delete the alias if that does not work.

It may be that it works in some cases and that there is something specific about this situation which causes the error.

Steps To Reproduce

To reproduce the behavior:

1. Spin up a new site
2. Try to create a layout with path set for “about”
3. See red alert and click on link “Delete the alias first”
4. Confirm
5. White screen

Actual behavior

See above

Expected behavior

That either the link for "delete the alias works" or people are not given this option.

Additional information

Tested this with BackdropCMS.org demo site.

I discovered this bug while testing the PR for this issue: #1528