Validate route uri

Writeup and example: https://github.com/RyanBard/scg-npe

spring-cloud-gateway version: 2.0.0.M5 spring-boot-version: 2.0.0.M7

I'm getting a NullPointerException in NettyRoutingFilter on line 67 because scheme is null. It's possible that my configuration in my application.yml is bogus (the uri and predicate Path do not match -- EDIT: I've verified that it still fails for the same reason even if they do overlap), however, it looks like the overwriting of scheme in the UriComponentsBuilder calls in RouteToRequestUrlFilter could be problematic in other situations.

I would appreciate if you could take a look.

Thank you