title: UITableView: contentOffset is changing automatically
body: <p>I have a UITableView with each cell containing a UICollectionView. Each cell can be expanded/collapsed. While doing so the tableView's contentOffset changes, which when goes negative causes a gap in the beginning of the tableView, making the first cell itself to start from half of the tableView.</p>
  
  <p>It seems to work properly for iOS 9, iOS 10 and iOS11.1.2. Only in case of iOS11.2.1, the issue is there.</p>
  
  <p>Can anyone help with the issue?</p>