ancestors() can loop

[nigelhorne]

I had a broken Gedcom where a person was their own parent. This caused a loop in G::I::ancestors(). It would have saved me a lot of time finding my mistake if the ancestors() method were to error if a person is their own ancestor.

[pjcj]

I think you're correct that we need to do something there. I don't think throwing an error is correct, but looping is certainly wrong.