src: use MaybeLocal.ToLocal instead of IsEmpty

PR-URL: https://github.com/nodejs/node/pull/35716


Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>