message: bitcoin transaction height can be null
diff: @@ -615,7 +615,7 @@ export class BitcoindAPI extends BitcoinNetwork {
  })
  .then(resp => resp.json())
  .then((respObj) => {
  - if (!respObj) {
  + if (!respObj || !respObj.result) {
  // unconfirmed
  throw new Error("Unconfirmed transaction")
  }
  