message: pass omitFilename to stop sending filename=undefined
diff: @@ -243,6 +243,7 @@ function uploadFile(matrixClient, roomId, file, progressHandler) {
  const blob = new Blob([encryptResult.data]);
  return matrixClient.uploadContent(blob, {
  progressHandler: progressHandler,
  + omitFilename: true,
  }).then(function(url) {
  // If the attachment is encrypted then bundle the URL along
  // with the information needed to decrypt the attachment and
  