RFR(XS): 8209736: runtime/RedefineTests/ModifyAnonymous.java fails with NullPointerException when running in CDS mode

[Calvin Cheung]

bug: https://bugs.openjdk.java.net/browse/JDK-8209736

webrev: http://cr.openjdk.java.net/~ccheung/8209736/webrev.00/

The test failure is no longer reproducible; it happened only once in 
tier3 and once in tier6 testing.
This simple change is just adding a null check on the variable clazz and 
prints the array size and index if it is null.

Testing: hs-tier{1,2,3} with default CDS archive in JDK.

thanks,
Calvin