[3.7] bpo-33383: Fix crash in get() of the dbm.ndbm database object. (GH-6630) (GH-6631)

(cherry picked from commit 2e38cc39330bd7f3003652869b644110a97a78d8)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
7 files changed