I am using the foloowing api for fetching the playlist of youtube channel: https://www.googleapis.com/youtube/v3/playlistItems?key=*********************&playlistId=PLtS_xRaINoXVqR9JTzwkcMLaOIq0uj831&part=snippet,contentDetails&format=6&maxResults=50&fields=items
some of the videos is not available so how can i exclude those videos ?