Previous behavior was to assume an error is a proper error in the
repl module. A check was added to not terminate the process on thrown
repl errors that are `null` or `undefined`.
PR-URL: https://github.com/nodejs/node/pull/14306
Fixes: https://github.com/nodejs/node/issues/12373
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com
