QFuture::isValid() without result

QFuture::isValid() returns true as soon as QPromise::start() has been called. According to the documentation this is false behavior:

"bool QFuture::isValid() const

Returns true if a result or results can be accessed or taken from this QFuture object. Returns false after the result was taken from the future."

As you can see in my attached excample future.isValid = true and future.resultCount() = 0 at the same time.

When trying to take a result then the thread blocks.