Fixed a subtle flaw in the GenericDelegator.findOne method. When a database query returns no result, GenericValue.NULL_VALUE is put in the pk cache - so future findOne calls will know the entity value doesn't exist. But the findOne method never checked for GenericValue.NULL_VALUE in cache gets, so the database was queried again for an entity value we already know doesn't exist.

https://issues.apache.org/jira/browse/OFBIZ-5332


git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1527626 13f79535-47bb-0310-9956-ffa450edef68