[3.14] gh-148390: fix undefined behavior of `memoryview(...).cast("?")` (GH-148454) (GH-148667)

(cherry picked from commit 69e0a78e6edc3166c7a5b166955c0cefd1bacd5d)

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>