title: TYPO3 repository->add not works
body: <p>I have TYPO3 version 7.6.18</p>
  
  <pre><code>$newMessage = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('Istar\\Femessages\\Domain\\Model\\Message');
                  $newMessage-&gt;setUserFrom($myUid);
                  $newMessage-&gt;setUserTo($userTo);
                  $newMessage-&gt;setChainUid($messageChainUid);
                  $newMessage-&gt;setMessage($message);
                  $this-&gt;messageRepository-&gt;add($newMessage);
                  $persistenceManager = $this-&gt;objectManager-&gt;get("TYPO3\\CMS\\Extbase\\Persistence\\Generic\\PersistenceManager");
                  $persistenceManager-&gt;persistAll();
  </code></pre>
  
  <p>Repository does't add new to DB without </p>
  
  <pre><code>            $persistenceManager = $this-&gt;objectManager-&gt;get("TYPO3\\CMS\\Extbase\\Persistence\\Generic\\PersistenceManager");
              $persistenceManager-&gt;persistAll();
  </code></pre>
  
  <p>Tell me please, why ? </p>