message: Add signature check
diff: /**
  * @prettier
  */
  +import * as _ from 'lodash';
  import * as Bluebird from 'bluebird';
  -
  const tronWeb = require('tronweb');
  import { BaseCoin as StaticsBaseCoin } from '@bitgo/statics';
  @@ -140,6 +140,9 @@ export class Trx extends BaseCoin {
  const tx = params.txPrebuild.transaction;
  // this prv should be hex-encoded
  const halfSigned = tronWeb.utils.crypto.signTransaction(params.prv, tx);
  + if (_.isEmpty(halfSigned.signature)) {
  + throw new Error('failed to sign transaction');
  + }
  return { halfSigned };
  }
  