tls: re-allow falsey option values

5723c4c5 was an unintentional breaking change in that it changed
the behaviour of `tls.createSecureContext()` to throw on false-y input
rather than ignoring it. This breaks real-world applications like `npm`.

This restores the previous behaviour.

PR-URL: https://github.com/nodejs/node/pull/15131
Ref: https://github.com/nodejs/node/pull/15053


Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: MichaëZasso <targos@protonmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>