Returning null matches the other providers and can avoid some expensive merges

git-svn-id: https://svn.apache.org/repos/asf/cxf/trunk@1444957 13f79535-47bb-0310-9956-ffa450edef68
Get one of Jason's tests working.

git-svn-id: https://svn.apache.org/repos/asf/cxf/trunk@1444958 13f79535-47bb-0310-9956-ffa450edef68