Fixed Plex Library Updates

(cherry picked from commit bd70fa54107c225ea08da53183e2be944e730475)

Closes #2757

src/NzbDrone.Core/Notifications/Plex/Server/PlexSectionItem.cs

@@ -6,9 +6,10 @@ namespace NzbDrone.Core.Notifications.Plex.Server
     public class PlexSectionItem
     {
         [JsonProperty("ratingKey")]
-        public int Id { get; set; }
+        public string Id { get; set; }
 
         public string Title { get; set; }
+        public string Guid { get; set; }
     }
 
     public class PlexSectionResponse
@@ -26,5 +27,10 @@ namespace NzbDrone.Core.Notifications.Plex.Server
     {
         [JsonProperty("_children")]
         public List<PlexSectionItem> Items { get; set; }
+
+        public PlexSectionResponseLegacy()
+        {
+            Items = new List<PlexSectionItem>();
+        }
     }
 }