xyzwriter: fixed warning
xyzwriter: fixed warning

MrTheodor/csg,votca/csg,votca/csg,MrTheodor/csg,MrTheodor/csg,MrTheodor/csg,votca/csg,MrTheodor/csg,votca/csg,junghans/csg,junghans/csg,junghans/csg,junghans/csg,junghans/csg,junghans/csg