removed some findBugs warnings

Change-Id: Ieb127835caa6f45e8ae94ef2fde33fa9a744da46
Reviewed-on: http://gerrit.esdi-community.eu/3225
Tested-by: Jenkins <sitemple@igd.fraunhofer.de>
Reviewed-by: Simon Templer <simon.templer@igd.fraunhofer.de>