lib: re-fix v8_prof_processor

Make the script not error out immediately because of a missing
pseudo-global.
(Note that it seems like tests are still broken on `master`.)

PR-URL: https://github.com/nodejs/node/pull/19059
Fixes: https://github.com/nodejs/node/issues/19044
Refs: https://github.com/nodejs/node/pull/18623


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matheus Marchini <matheus@sthima.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>