title: Core Data: model is nil while modelURL is valid
body: <p><code>__managedObjectModel</code> is nil even modelURL exists. There is <a href="https://stackoverflow.com/questions/6750156/nsmanagedobjectmodel-initwithcontentsofurl-returns-nil-eventhough-the-modelurl-i">a similar post</a>, but the accepted answer (rename model file and relaunch Xcode) doesn't work for me. </p>
  
  <pre><code>- (NSManagedObjectModel *)managedObjectModel
  {
      if (__managedObjectModel != nil) {
          return __managedObjectModel;
      }
      NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Failed" withExtension:@"momd"];
  
      __managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
  
      return __managedObjectModel;
  }
  </code></pre>
  
  <p>I po <code>modelURL</code> in console</p>
  
  <pre><code>(lldb) po modelURL
  (NSURL *) $4 = 0x088832f0 file://localhost/Users/philip/Library/Application%20Support/iPhone%20Simulator/5.1/Applications/9E59167C-8D9E-4ADE-BBD7-0BE9A33A6A86/Failed.app/Failed.momd/
  </code></pre>