worker: handle exception when creating execArgv errors

Handle possible JS exceptions that can occur by returning to JS land
immediately.

The motivation for this change is that `USE(….FromJust());` is an
anti-pattern, and `.FromJust()` with an unused return value is
superseded by `.Check()`. However, in this case, checking that the
operation succeeded is not necessary.

Refs: https://github.com/nodejs/node/pull/27162

PR-URL: https://github.com/nodejs/node/pull/27245


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>