rpc: don't return an error if no payments exist for ListPayments
rpc: don't return an error if no payments exist for ListPayments

aakselrod/lnd,AndrewSamokhvalov/lnd,LightningNetwork/lnd,LightningNetwork/lnd,ddustin/lnd,AndrewSamokhvalov/lnd,ddustin/lnd,aakselrod/lnd