Otherwise, this condition would result in an error that just reads
`cb is not a function`, and which additionally could have lost
stack trace context through a `process.nextTick()` call.
PR-URL: https://github.com/nodejs/node/pull/19510
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
