message: when the connection is cut the result seems to be undefined rather than an error, treating as retry fixes
diff: @@ -245,6 +245,9 @@ export default class ExtCommand {
  { frameId: top ? 0 : frameId }
  )
  .then(r => {
  + if (!r) {
  + throw new Error('result is undefined')
  + }
  return r
  })
  .catch(error => {
  