尝试插入新单元格时,UICollectionView中出现NSInternalConferenceException

我正试图在_myMusicCollectionView中插入一个新单元格。数据源是SharedAppDelegate.myMusics数组:

[_myMusicsCollectionView performBatchUpdates:^{
                                [SharedAppDelegate.myMusics addObject:c.item];
                                [_myMusicsCollectionView insertItemsAtIndexPaths:[[NSArray alloc] initWithObjects:[NSIndexPath indexPathForRow:SharedAppDelegate.myMusics.count-1 inSection:0], nil]];
                            } completion:^(BOOL finished) {
                                [_musicStoreCollectionView reloadItemsAtIndexPaths:[[NSArray alloc] initWithObjects:indPath, nil]];
                            }];

我得到了:

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'request for index path for global index 805306367 when there are only 1 items in the collection view'

我哪里错了?