message: fix buffer detection for browser
  Summary:
  Reviewers: tyler, bigly, andrew
  Subscribers: ben
diff: @@ -470,7 +470,7 @@ Btc.prototype.verifySignature = function(transaction, inputIndex, amount, verifi
  let isSignatureValid = false;
  - if (_.isBuffer(signatureBuffer)) {
  + if (Buffer.isBuffer(signatureBuffer) && signatureBuffer.length > 0) {
  // slice the last byte from the signature hash input because it's the hash type
  const signature = bitcoin.ECSignature.fromDER(signatureBuffer.slice(0, -1));
  const hashType = _.last(signatureBuffer);
  