pythongh-99240: Reset pointer to NULL when the pointed memory is freed in argument parsing (python#99890)

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

Author: 3 people