fix for nil preferences
fix for nil preferences

it will cause error on default_preferences.merge(preferences) when preferences is nil
DarkoP/spree,ayb/spree,orenf/spree,ayb/spree,jaspreet21anand/spree,abhishekjain16/spree,dafontaine/spree,abhishekjain16/spree,vinsol/spree,siddharth28/spree,DarkoP/spree,ayb/spree,ayb/spree,berkes/spree,DarkoP/spree,brchristian/spree,berkes/spree,orenf/spree,dafontaine/spree,maybii/spree,abhishekjain16/spree,dafontaine/spree,jaspreet21anand/spree,calvinl/spree,azranel/spree,siddharth28/spree,siddharth28/spree,pulkit21/spree,berkes/spree,brchristian/spree,vmatekole/spree,vmatekole/spree,brchristian/spree,zaeznet/spree,orenf/spree,azranel/spree,zaeznet/spree,azranel/spree,vinsol/spree,jaspreet21anand/spree,vmatekole/spree,calvinl/spree,gautamsawhney/spree,DarkoP/spree,siddharth28/spree,dafontaine/spree,zaeznet/spree,brchristian/spree,maybii/spree,calvinl/spree,maybii/spree,gautamsawhney/spree,calvinl/spree,imella/spree,vinsol/spree,maybii/spree,vinayvinsol/spree,pulkit21/spree,imella/spree,orenf/spree,gautamsawhney/spree,vinsol/spree,zaeznet/spree,vmatekole/spree,vinayvinsol/spree,abhishekjain16/spree,gautamsawhney/spree,pulkit21/spree,imella/spree,azranel/spree,vinayvinsol/spree,vinayvinsol/spree,berkes/spree,jaspreet21anand/spree,pulkit21/spree