fix hasMediaSources exception

MediaBrowser.Server.Implementations/Session/SessionManager.cs

@@ -305,7 +305,7 @@ namespace MediaBrowser.Server.Implementations.Session
             }
         }
 
-        private async Task<MediaSourceInfo> GetMediaSource(BaseItem item, string mediaSourceId)
+        private async Task<MediaSourceInfo> GetMediaSource(IHasMediaSources item, string mediaSourceId)
         {
             var sources = await _mediaSourceManager.GetPlayackMediaSources(item.Id.ToString("N"), false, CancellationToken.None)
                         .ConfigureAwait(false);
@@ -334,12 +334,17 @@ namespace MediaBrowser.Server.Implementations.Session
                 {
                     var runtimeTicks = libraryItem.RunTimeTicks;
 
-                    var mediaSource = await GetMediaSource(libraryItem, info.MediaSourceId).ConfigureAwait(false);
+                    MediaSourceInfo mediaSource = null;
+                    var hasMediaSources = libraryItem as IHasMediaSources;
+                    if (hasMediaSources != null)
+                    {
+                        mediaSource = await GetMediaSource(hasMediaSources, info.MediaSourceId).ConfigureAwait(false);
 
                         if (mediaSource != null)
                         {
                             runtimeTicks = mediaSource.RunTimeTicks;
                         }
+                    }
 
                     info.Item = GetItemInfo(libraryItem, libraryItem, mediaSource);
 
@@ -756,7 +761,13 @@ namespace MediaBrowser.Server.Implementations.Session
 
                 if (current == null || !string.Equals(current.Id, info.ItemId, StringComparison.OrdinalIgnoreCase))
                 {
-                    var mediaSource = await GetMediaSource(libraryItem, info.MediaSourceId).ConfigureAwait(false);
+                    MediaSourceInfo mediaSource = null;
+
+                    var hasMediaSources = libraryItem as IHasMediaSources;
+                    if (hasMediaSources != null)
+                    {
+                        mediaSource = await GetMediaSource(hasMediaSources, info.MediaSourceId).ConfigureAwait(false);
+                    }
 
                     info.Item = GetItemInfo(libraryItem, libraryItem, mediaSource);
                 }