RFR 8246193: Possible NPE in ENC-PA-REP search in AS-REQ

[Weijun Wang]

Please take a review at

   http://cr.openjdk.java.net/~weijun/8246193/webrev.00/

While searching for ENC-PA-REP in the PA-DATA list of AS-REQ, it's possible 
there is no PA-DATA at all. This could happen when preauth is turned off.

Thanks,
Max