/**
  * Sets panel state to beginning (currentState => empty) and removes all votes from all votingOptions from all votings
  *
  * @param Panel $panel
  * @throws \TYPO3\CMS\Extbase\Persistence\Exception\IllegalObjectTypeException
  */
 protected function resetPanel(Panel $panel)
 {
     $panel->setCurrentState('');
     foreach ($panel->getVotings() as $voting) {
         /** @var $voting \Visol\EasyvoteEducation\Domain\Model\Voting */
         foreach ($voting->getVotingOptions() as $votingOption) {
             /** @var $votingOption \Visol\EasyvoteEducation\Domain\Model\VotingOption */
             $votingOption->getVotes()->removeAll($votingOption->getVotes());
             $this->votingOptionRepository->update($votingOption);
         }
     }
     $this->persistenceManager->persistAll();
 }