fix an issue about determining 'IsSecondaryAudio'

fix an issue that could not correctly determine 'IsSecondaryAudio' in some cases.

MediaBrowser.Model/Dto/MediaSourceInfo.cs

@@ -209,10 +209,7 @@ namespace MediaBrowser.Model.Dto
             {
                 if (currentStream.Type == MediaStreamType.Audio && currentStream.IsDefault)
                 {
-                    if (currentStream.Index != stream.Index)
-                    {
-                        return true;
-                    }
+                    return currentStream.Index != stream.Index;
                 }
             }