Add allow_nil to numericality validation in refund
Add allow_nil to numericality validation in refund

calvinl/spree,berkes/spree,orenf/spree,orenf/spree,brchristian/spree,imella/spree,dafontaine/spree,azranel/spree,brchristian/spree,ayb/spree,siddharth28/spree,abhishekjain16/spree,jaspreet21anand/spree,jaspreet21anand/spree,berkes/spree,gautamsawhney/spree,berkes/spree,orenf/spree,jaspreet21anand/spree,gautamsawhney/spree,abhishekjain16/spree,azranel/spree,vinsol/spree,vinayvinsol/spree,berkes/spree,DarkoP/spree,siddharth28/spree,zaeznet/spree,maybii/spree,pulkit21/spree,ayb/spree,imella/spree,pulkit21/spree,maybii/spree,gautamsawhney/spree,dafontaine/spree,zaeznet/spree,ayb/spree,dafontaine/spree,vmatekole/spree,orenf/spree,ayb/spree,siddharth28/spree,vinayvinsol/spree,calvinl/spree,siddharth28/spree,dafontaine/spree,zaeznet/spree,jaspreet21anand/spree,maybii/spree,maybii/spree,vinsol/spree,pulkit21/spree,abhishekjain16/spree,vmatekole/spree,vinayvinsol/spree,azranel/spree,vinayvinsol/spree,brchristian/spree,azranel/spree,pulkit21/spree,DarkoP/spree,abhishekjain16/spree,vmatekole/spree,gautamsawhney/spree,vinsol/spree,zaeznet/spree,calvinl/spree,imella/spree,DarkoP/spree,brchristian/spree,vmatekole/spree,DarkoP/spree,calvinl/spree,vinsol/spree