v8::MaybeLocal::ToLocalChecked() will abort on an empty handle.
AsyncWrap::MakeCallback returns an empty handle if the domain is
disposed, but this should not cause the process to abort. So instead
return v8::Undefined() and allow the error to be handled normally.
PR-URL: https://github.com/nodejs/node/pull/14722
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>
