Add workaround for collection view problems with adding/removing last items in a section

[toto]

See also: https://github.com/AshFurrow/UICollectionView-NSFetchedResultsController/blob/master/AFMasterViewController.m#L222

[anagromataf]

@toto what exactly is the problem? I try do reproduce it with the demo app. There it is possible to add an item to an empty section or remove the last item of a section.

[anagromataf]

This will never happen, as a fetched results controller will never return a section without an item.