title: Magical Record persistance issue
body: <p>I have following Problem:</p>
  
  <p>First up... i use MagicalRecord for the whole CoreData thing</p>
  
  <ul>
  <li>I have two Entities: A and B</li>
  <li>They have a relation between each other</li>
  <li>I create one instance of Entity A</li>
  <li>I create several instances ob Entity B and set the relation</li>
  <li>I don't call [[NSManagedObjectContext defaultContext] save];
  <ul>
  <li>It's fine</li>
  <li>The relation is ok... I can check it using the findByAttribute method</li>
  </ul></li>
  <li>If I call this save then the relation is destroyed...
  <ul>
  <li>the same check using findByAttribute does not find results any more</li>
  </ul></li>
  </ul>
  
  <p>I have absolutely no clue what I am doing wrong or if it's a bug in CoreData / MagicalRecord...</p>
  
  <p>I made a sample project showing the problem.
  <a href="https://github.com/bliblablo/MagicalRecordsProblem" rel="nofollow">https://github.com/bliblablo/MagicalRecordsProblem</a></p>
  
  <p>You can see the problem by following this steps:</p>
  
  <ul>
  <li>click "create"</li>
  <li>click "add"</li>
  <li>click "check"</li>
  <li>see the log output for results</li>
  <li>click "save"</li>
  <li>click "check" again and see the problem in the log :)</li>
  </ul>
  
  <p>Any help is really appreciated!!!
  Thanks a lot!</p>