Do not include refundAddressTransactions object if null
Do not include refundAddressTransactions object if null

OpenBazaar/openbazaar-go,OpenBazaar/openbazaar-go,hoffmabc/openbazaar-go,gubatron/openbazaar-go,duomarket/openbazaar-test-nodes,gubatron/openbazaar-go,hoffmabc/openbazaar-go,gubatron/openbazaar-go,OpenBazaar/openbazaar-go,hoffmabc/openbazaar-go,duomarket/openbazaar-test-nodes,duomarket/openbazaar-test-nodes