title: Custom collection view layout leaves dirty screenshot of cell on selection
body: <p>I am pretty new to implement a custom collection view layout. </p>
  
  <p>The layout contains cells with size of screen's width and height, like a photo gallery view. But when I select a cell the <code>didSelectItemAtIndexPath:(NSIndexPath *)indexPath</code> method runs and, opens a new view. But after closing that view I cannot select that cell again. Then after scrolling the collection view and I can see that the selected cell left a screenshot like thing in collection view. I could not understand what is the problem. I tried to invalidate the layout but nothing happened.</p>
  
  <p>Hope you can help. Thanks in advance.</p>
  
  <p>PS: I can provide code but I don't know what to provide. Ask, then I will share.</p>
  
  <p>Update 1:</p>
  
  <pre><code>User *user = [_users objectAtIndex:indexPath.row];
  ProfileViewController *pvc = [[ProfileViewController alloc] initWithUser:user];
  [self presentViewController:pvc animated:true completion:nil];
  </code></pre>
  
  <p>Update 2: </p>
  
  <p>I tried to add a button in UICollectionViewCell and tried to open the ProfileView on tap of this button and it works as expected with no problem. So, I guess problem seems in custom view layout.</p>