keep playstate during syncplay group creation

MediaBrowser.Model/SyncPlay/JoinGroupRequest.cs

@@ -12,11 +12,5 @@ namespace MediaBrowser.Model.SyncPlay
         /// </summary>
         /// <value>The Group id to join.</value>
         public Guid GroupId { get; set; }
-
-        /// <summary>
-        /// Gets or sets the playing item id.
-        /// </summary>
-        /// <value>The client's currently playing item id.</value>
-        public Guid PlayingItemId { get; set; }
     }
 }