[3.9] bpo-41215: Don't use NULL by default in the PEG parser keyword list (GH-21355) (GH-21356)



(cherry picked from commit 39e76c0fb07e20acad454deb86a0457b279884a9)

Co-authored-by: Pablo Galindo <pablogsal@gmail.com>

Automerge-Triggered-By: @lysnikolaou
4 files changed