ncd: Fix crash with num_multiply(..., "0").
ncd: Fix crash with num_multiply(..., "0").

linfengfeiye/badvpn,binondord/badvpn,linfengfeiye/badvpn,Git-Host/badvpn,binondord/badvpn,PowerOlive/badvpn,Git-Host/badvpn,Git-Host/badvpn,PowerOlive/badvpn,linfengfeiye/badvpn,LazyZhu/badvpn,binondord/badvpn,binondord/badvpn,LazyZhu/badvpn,Git-Host/badvpn,PowerOlive/badvpn,tempbottle/badvpn,PowerOlive/badvpn,LazyZhu/badvpn,tempbottle/badvpn,linfengfeiye/badvpn,tempbottle/badvpn,binondord/badvpn,PowerOlive/badvpn,LazyZhu/badvpn,tempbottle/badvpn,Git-Host/badvpn,LazyZhu/badvpn,linfengfeiye/badvpn,tempbottle/badvpn