Fix gcc compiler warning about comparing unsigned and signed.
Fix gcc compiler warning about comparing unsigned and signed.

seec-team/seec,mheinsen/seec,mheinsen/seec,seec-team/seec,seec-team/seec,mheinsen/seec,mheinsen/seec,seec-team/seec,seec-team/seec,mheinsen/seec