Only set expiration days if they exist
Only set expiration days if they exist

Change-Id: I068aa9dfe020cb3ebe294cfac13dabe22d461f98

degica/spree-add-on,degica/spree-add-on,StemboltHQ/spree-add-on,shioyama/spree-add-on,freerunningtech/spree-add-on,shioyama/spree-add-on