test,worker: posting undefined/null message to message port

Related: https://github.com/nodejs/node/issues/26122

PR-URL: https://github.com/nodejs/node/pull/26123


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>