message: error appropriately if a tx is unconfirmed
diff: @@ -614,7 +614,15 @@ export class BitcoindAPI extends BitcoinNetwork {
  headers })
  })
  .then(resp => resp.json())
  - .then(respObj => ({ block_height: respObj.result.height }))
  + .then((respObj) => {
  + if (!respObj) {
  + // unconfirmed
  + throw new Error("Unconfirmed transaction")
  + }
  + else {
  + return { block_height: respObj.result.height }
  + }
  + })
  }
  getNetworkedUTXOs(address: string) : Promise<Array<UTXO>> {
  