src: handle NULL env scenario

PR-URL: https://github.com/nodejs/node/pull/32230


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matheus Marchini <mat@mmarchini.me>