Railo null support

I made some minor changes to be able to use TestBox for Railo with null support enabled. Nothing that would break compatibility when null support is off (or nonexistent).

When a function is called with named arguments, Railo passes null for the arguments that are not passed. With null support enabled this causes problems.

Thanks for considering this fix, and I'd be happy to hear your feedback.
Hi Ryan, I am loving this pull request, but have a question on this approach for checking arguments on the URL scope. Why is that necessary, wouldn't structkeyexists work as well on url?