In the case where triggerAsyncId is null it should default to the
current executionAsyncId. This worked but as a side-effect the resource
object was changed too.
This fix also makes the null check more strict. EmitInitS is not a
documented API, thus there is no reason to be flexible in its input.
Ref: https://github.com/nodejs/node/issues/13548#issuecomment-310985270
PR-URL: https://github.com/nodejs/node/pull/14026
Reviewed-By: Refael Ackermann <refack@gmail.com>
