请解决该Bug index = -1 Bug

[ShouBinCheng]

在真机情况向调用经常重现。index==-1 报僵尸内存错误在这一句

UICollectionViewLayoutAttributes * cellAttrs = [_collectionView layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:index inSection:0]];

app 启动时如下去reload 重现bug

dispatch_async(dispatch_get_main_queue(), ^{
     weakSelf.DataSource = newDataSource;//这里的count值由开始的0到大于0。
    [weakSelf.pagerBar reloadData];
});

修复

- (CGRect)cellFrameWithIndex:(NSInteger)index
{
    // ***修复
    if (index < 0) {
        return CGRectZero;
    }
    // ***
    if (index >= _countOfItems) {
        return CGRectZero;
    }
    UICollectionViewLayoutAttributes * cellAttrs = [_collectionView layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:index inSection:0]];
    if (!cellAttrs) {
        return CGRectZero;
    }
    return cellAttrs.frame;
}