[9] code review request for 8130799: KeyStoreSpi.engineProbe does not throw the expected NullPointerException

[Vincent Ryan]

Please review this trivial change to the KeyStoreSpi.engineProbe method so that 
it matches its specification wrt NPE.
Thanks.

Bug: https://bugs.openjdk.java.net/browse/JDK-8130799 
<https://bugs.openjdk.java.net/browse/JDK-8130799>
Webrev: http://cr.openjdk.java.net/~vinnie/8130799/webrev.00/ 
<http://cr.openjdk.java.net/~vinnie/8130799/webrev.00/>