Fix possible nullref

Emby.Server.Implementations/ApplicationHost.cs

@@ -121,6 +121,8 @@ namespace Emby.Server.Implementations
     /// </summary>
     public abstract class ApplicationHost : IServerApplicationHost, IDisposable
     {
+        private SqliteUserRepository _userRepository;
+
         /// <summary>
         /// Gets a value indicating whether this instance can self restart.
         /// </summary>
@@ -291,8 +293,6 @@ namespace Emby.Server.Implementations
         /// <value>The user data repository.</value>
         private IUserDataManager UserDataManager { get; set; }
 
-        private IUserRepository UserRepository { get; set; }
-
         internal SqliteItemRepository ItemRepository { get; set; }
 
         private INotificationManager NotificationManager { get; set; }
@@ -766,9 +766,9 @@ namespace Emby.Server.Implementations
             AuthenticationRepository = GetAuthenticationRepository();
             serviceCollection.AddSingleton(AuthenticationRepository);
 
-            UserRepository = GetUserRepository();
+            _userRepository = GetUserRepository();
 
-            UserManager = new UserManager(LoggerFactory, ServerConfigurationManager, UserRepository, XmlSerializer, NetworkManager, () => ImageProcessor, () => DtoService, this, JsonSerializer, FileSystemManager);
+            UserManager = new UserManager(LoggerFactory, ServerConfigurationManager, _userRepository, XmlSerializer, NetworkManager, () => ImageProcessor, () => DtoService, this, JsonSerializer, FileSystemManager);
             serviceCollection.AddSingleton(UserManager);
 
             LibraryManager = new LibraryManager(this, LoggerFactory, TaskManager, UserManager, ServerConfigurationManager, UserDataManager, () => LibraryMonitor, FileSystemManager, () => ProviderManager, () => UserViewManager);
@@ -961,8 +961,8 @@ namespace Emby.Server.Implementations
         /// <summary>
         /// Gets the user repository.
         /// </summary>
-        /// <returns>Task{IUserRepository}.</returns>
-        private IUserRepository GetUserRepository()
+        /// <returns><see cref="Task{SqliteUserRepository}" />.</returns>
+        private SqliteUserRepository GetUserRepository()
         {
             var repo = new SqliteUserRepository(LoggerFactory, ApplicationPaths, JsonSerializer);
 
@@ -1910,11 +1910,9 @@ namespace Emby.Server.Implementations
                     }
                 }
 
-                UserRepository.Dispose();
+                _userRepository?.Dispose();
             }
 
-            UserRepository = null;
-
             _disposed = true;
         }
     }