when corruption strikes, don't create exceptions with circular references

Yes, the situation, as noted in the comment is this:

e = SomeException
ce = ExceptionsHelper.unwrap(e, CorruptIndexException.class)

when current was 'null' for the CAS operation, we know that either ce == e or that ce is the root cause of e that was unwrapped, so we cannot ce.addSuppressed(e) or it creates a cycle.