[misc] Fixed some Sonar findings

- Use of System.*.println instead of propert logging
- Null-safety of Predicate.apply(...)

Change-Id: I97b64d3d975bb22a1705b123a61f281423341fe8
Signed-off-by: Andreas Sewe <andreas.sewe@codetrails.com>
Merge "[misc] Fixed some Sonar findings"