title: iOS MPMediaQuery.artistsQuery() doesn't return every artist if compilation is checked
body: <p>I have been writing a music app using Swift 2.3.  The trouble that I've found is that my a MPMediaQuery.artistsQuery() doesn't provide all of the artists.  Using iTunes, I've tracked it down to if "Album is a compilation of songs by various artists" is checked, then that artist will not show up in my tableView.  For example, one of the CD's (which doesn't show up in my tableView) that I imported using iTunes is: Little River Band, Greatest Hits.  iTunes seems to think that it is a compilation of various artists, and while I disagree, I still need to handle the scenario.</p>
  
  <pre><code>var qryArtists = MPMediaQuery.artistsQuery()
  qryArtists.groupingType = MPMediaGrouping.Artist
  
  // Set the cell in the table
  func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -&gt; UITableViewCell {
  
      // I am using the custom class that I created called: myCustomArtistTableViewCell
      let cell = tableView.dequeueReusableCellWithIdentifier("artistIdCell", forIndexPath: indexPath) as! myCustomArtistTableViewCell
  
      let currLoc = qryArtists.collectionSections![indexPath.section].range.location
      let rowItem = qryArtists.collections![indexPath.row + currLoc]
  
      cell.artistTitle.text = rowItem.items[0].artist
  
      return cell
  }
  </code></pre>
  
  <p>All of the sections in the table are fine.  I am just missing a few artists including: Little River Band.</p>
  
  <p>Also, the artist tag on every song on my example album, contains the string: Little River Band.  I just can't seem to figure out why that artist and a few others are being excluded.  Thank you very much for any help.</p>