[3.9] gh-92112: Fix crash triggered by an evil custom `mro()` (GH-92113) (GH-92372)

(cherry picked from commit 85354ed78c0edb6d81a2bd53cabc85e547b8b26e)

Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>
3 files changed