[3.10] gh-99240: Reset pointer to NULL when the pointed memory is freed in argument parsing (GH-99890) (#100386)

(cherry picked from commit efbb1eb9f54cad4f7bf5df03eed3a6aba02d99f4)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>
Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>