Don't return a nil response for maven-metadata.xml sums [#515]
Don't return a nil response for maven-metadata.xml sums [#515]

This causes 400's to be returned for those files.

tobias/clojars-web,clojars/clojars-web,technomancy/clojars-web,nberger/clojars-web,tobias/clojars-web,nberger/clojars-web,technomancy/clojars-web,ato/clojars-web,ato/clojars-web,tobias/clojars-web,clojars/clojars-web,clojars/clojars-web