Hugo: Check 404 etc. IsAncestor vs the others

[bep]

See https://discourse.gohugo.io/t/runtime-error-calling-functions-on-section/23581

[onedrawingperday]

There are 3 themes in the themes repo that broke due to this bug.

See: https://github.com/gohugoio/hugoThemes/issues/810

[bep]

It would probably be worth the effort to somehow get the themes build for master as a CI build, somehow. I will think about it.

[tshort]

Docsy has an IsDescendant issue with 0.65.x, so it might be the same as this. I don't know why it didn't get caught in https://github.com/gohugoio/hugoThemes/issues/810.

https://github.com/google/docsy/issues/210

[onedrawingperday]

I don't know why it didn't get caught in gohugoio/hugoThemes#810.

See the rather long discussion at https://github.com/gohugoio/hugoThemes/issues/650 for the answer.