fix NaN issue, add default obj if missing from itemDef, do min 100% for artifact not class item
fix NaN issue, add default obj if missing from itemDef, do min 100% for artifact not class item

this fixes #581

chrisfried/DIM,chrisfried/DIM,bhollis/DIM,48klocs/DIM,48klocs/DIM,48klocs/DIM,LouisFettet/DIM,delphiactual/DIM,LouisFettet/DIM,delphiactual/DIM,DestinyItemManager/DIM,chrisfried/DIM,delphiactual/DIM,bhollis/DIM,bhollis/DIM,DestinyItemManager/DIM,DestinyItemManager/DIM,bhollis/DIM,delphiactual/DIM,DestinyItemManager/DIM,chrisfried/DIM