fix issue when inserting the first object or deleting the last object

This is to prevent a bug in UICollectionView from occurring.
The bug presents itself when inserting the first object or deleting the
last object in a collection view.
http://stackoverflow.com/questions/12611292/uicollectionview-assertion-f
ailure
This logic should be removed once the bug has been fixed, it is tracked
in OpenRadar
http://openradar.appspot.com/12954582