title: UICollectionView must be initialized with a non-nil layout parameter
body: <p>I'm new to <code>UICollectionView</code> and I'm following a tutorial I found on the web but I'm stuck on an error I can't figure out. Here's a bit of context. </p>
  
  <p>In the debugger I can see that following is happening: </p>
  
  <ul>
  <li><code>numberOfSectionsInCollectionView</code>: is called and I return 1</li>
  <li><code>collectionView:numberOfItemsInSection:</code> is called and I return the size of the model (20)</li>
  <li><code>collectionView:layout:sizeForItemAtIndexPath:</code> gets called once for each item in the model</li>
  <li><code>collectionView:layout:insetForSectionAtIndex:</code> is called</li>
  <li><p><code>collectionView:cellForItemAtIndexPath:</code> gets called and it crashes on this line...</p>
  
  <pre><code>UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MyCell" forIndexPath:indexPath];
  </code></pre></li>
  </ul>
  
  <p>with this error...</p>
  
  <pre><code>*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'UICollectionView must be initialized with a non-nil layout parameter'
  </code></pre>
  
  <p>When I pause execution on that line and check the console it appears that there is a layout...</p>
  
  <pre><code>(lldb) po collectionView.collectionViewLayout
  (UICollectionViewLayout *) $4 = 0x07180fd0 &lt;UICollectionViewFlowLayout: 0x7180fd0&gt;
  </code></pre>
  
  <p>The <code>UICollectionView</code> is part of the one and only scene in the storyboard. In viewController.m there are no other <code>UICollectionView</code>s created by any means. </p>
  
  <p>Does anyone have any ideas? </p>