Fix for animated insert in collection view 

@joe-goullaud Small fix

It turns out that collection views don't like it when you do a batch update that includes inserting a section and then inserting objects into that same section. That's one source of the mysterious "stuck" cells that never go away. This is just a tiny fix to prevent the object inserts into newly inserted sections as part of the same batch of updates.

May also apply to table views, haven't tested it yet, though I haven't seen this come up.