csg_stat: don't normalize bonded distributions if the norm is 0
csg_stat: don't normalize bonded distributions if the norm is 0

vaidyanathanms/votca.csg,Pallavi-Banerjee21/votca.csg,Pallavi-Banerjee21/votca.csg,vaidyanathanms/votca.csg,Pallavi-Banerjee21/votca.csg,Pallavi-Banerjee21/votca.csg,vaidyanathanms/votca.csg,vaidyanathanms/votca.csg,Pallavi-Banerjee21/votca.csg,vaidyanathanms/votca.csg,Pallavi-Banerjee21/votca.csg