Added some more test cases for null and empty string tests.
Added some more test cases for null and empty string tests.

It appears that tests for equality or non-equality to null are not working.


git-svn-id: de0229a90a04588cc4459530912ec55932f3d65c@136499 13f79535-47bb-0310-9956-ffa450edef68

apache/commons-jexl,apache/commons-jexl,apache/commons-jexl