Request for Review: 8035973: NPE in ForwardBuilder

[Jason Uh]

Could I please get a review of this change?

Just a simple fix for 7u-dev that adds a check for a null CertStore, in 
case URICertStore.getInstance returns null.

webrev: http://cr.openjdk.java.net/~juh/8035973/webrev.00/
bug: http://bugs.openjdk.java.net/browse/JDK-8035973

noreg-sqe because an SQE test is already in place.

Thanks,
Jason