In 862c395d3263f30057aef73a14704345e181dde3, SendingErrorHandler was
refactored to replace the `\MailPoet\Tasks\Sending` class with Doctrine
code. Inside `processSoftError()`, a call to
`$sendingTask->saveSubscriberError()` was replaced with a call to
`$this->scheduledTaskSubscribersRepository->saveError()`. The problem is
that the former updates the processed and unprocessed counts in the
QueueEntity while the later doesn't.
This commit fixes this issue by calling
`$this->sendingQueuesRepository->updateCounts()` inside
`processSoftError()`.
[MAILPOET-5682]
