[OPENENGSB-3761] handle null values correctly
[OPENENGSB-3761] fix review issues
Merge pull request #900 from thrau/master

Checkstyle fixes and license headers related to ldap usersync code
Merge pull request #898 from stfnsche/master

[OPENENGSB-3761] handle null values correctly
[OPENENGSB-3774] Fix checkstyle errors in RequestHandlerImpl and Test code