fix concurrency issue in base app host

MediaBrowser.Common.Implementations/BaseApplicationHost.cs

@@ -381,6 +381,7 @@ namespace MediaBrowser.Common.Implementations
                 if (disposable != null)
                 {
                     Logger.Info("Registering " + disposable.GetType().Name);
+
                     DisposableParts.Add(disposable);
                 }
             }
@@ -457,9 +458,12 @@ namespace MediaBrowser.Common.Implementations
             var parts = AllConcreteTypes.AsParallel().Where(currentType.IsAssignableFrom).Select(CreateInstance).Cast<T>().ToArray();
 
             if (manageLiftime)
+            {
+                lock (DisposableParts)
                 {
                     DisposableParts.AddRange(parts.OfType<IDisposable>());
                 }
+            }
 
             return parts;
         }