Signal QFutureWatcher::resultReadyAt (int) not emitted in some cases.

In QtConcurrent module. In case of using QFutureWatcher<void> to monitor progress of QFuture<void> future = QtConcurrent::map() signal resultReadyAt(int) for some reason not emitted.
Signals QFutureWatcher::started() and QFutureWatcher::finished() continue to work. Same piece of code using QFutureWatcher<int> to monitor QFuture<int>::mapped() work just fine.