finish removing ChannelFolderItem

MediaBrowser.Controller/Channels/Channel.cs

@@ -3,6 +3,7 @@ using MediaBrowser.Model.Channels;
 using MediaBrowser.Model.Querying;
 using System;
 using System.Linq;
+using System.Runtime.Serialization;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -30,6 +31,13 @@ namespace MediaBrowser.Controller.Channels
             return base.IsVisible(user);
         }
 
+        [IgnoreDataMember]
+        public override SourceType SourceType
+        {
+            get { return SourceType.Channel; }
+            set { }
+        }
+
         public override async Task<QueryResult<BaseItem>> GetItems(InternalItemsQuery query)
         {
             try