title: Collectionview performBatchUpdates crash
body: <p>I am trying to add new items to my collection view using insertItemsAtIndexPaths. My app crashes at performBatchupdate</p>
  
  <pre class="lang-Objective-C prettyprint-override"><code>- (void) addItems {
      NSArray *newProducts = @[@"1",@"2",@"3",@"4"];
      [self.collectionView performBatchUpdates:^{
          NSMutableArray *arrayWithIndexPaths = [NSMutableArray array];
          for (NSInteger index = self.array.count; index &lt; (self.array.count + newProducts.count); index++) {
              [arrayWithIndexPaths addObject:[NSIndexPath indexPathForRow:index inSection:0]];
          }
          [self.array addObjectsFromArray:newProducts];
          [self.collectionView insertItemsAtIndexPaths:arrayWithIndexPaths];
      }
                                    completion:nil];
  }
  </code></pre>
  
  <p>Following is the crash log:</p>
  
  <blockquote>
    <p><em>*</em> Assertion failure in -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:]</p>
  </blockquote>
  
  <p>This Assertion happens when cell is not registered with the collectionview. I am registering my cell.</p>