LUCENE-5666: fix some tests

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene5666@1594311 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5666: fix bug (null is no longer allowed)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene5666@1594316 13f79535-47bb-0310-9956-ffa450edef68