8067801: Enforce null check for underlying I/O streams

[Brian Burkhalter]

> On Jul 18, 2019, at 8:55 AM, Brian Burkhalter <brian.burkhalter at oracle.com> wrote:
> 
>> I see this is has pushed but I think it will need to be re-examined because the javadoc allows `in` and `out` to be specified as null and set after the stream is created (the javadoc for the parameters overrides the "Unless otherwise ..." text in the package description)
> 
> Argh. I guess you are correct.

Filed https://bugs.openjdk.java.net/browse/JDK-8228392 <https://bugs.openjdk.java.net/browse/JDK-8228392>.

Brian