fix build in jruby 9.0
fix build in jruby 9.0

I understand why it needed this, I don't understand how it worked in jruby 9.2 without it! Parser picadillos, this is better. The class doesn't get required so we can reference it until AFTER we call @indexer.reader_class, so we can't use the class itself in the assertion.

traject/traject