RFR(xs): 8202669: Intermittent crash in ClassLoadingService::compute_class_size()

[Calvin Cheung]

bug: https://bugs.openjdk.java.net/browse/JDK-8202669

webrev: http://cr.openjdk.java.net/~ccheung/8202669/webrev.00/

This bug surfaced after the change for JDK-8200466.
The proposed change is simply null checking the _transitive_interfaces 
before accessing its size().

I ran the affected tests with the change 30 times on Oracle platforms 
and didn't see any failures.

thanks,
Calvin