Wrap UseReactiveUI in RegisterResolverCallbackChanged

src/Avalonia.ReactiveUI/AppBuilderExtensions.cs

@@ -9,19 +9,22 @@ namespace Avalonia.ReactiveUI
     {
         /// <summary>
         /// Initializes ReactiveUI framework to use with Avalonia. Registers Avalonia 
-        /// scheduler and Avalonia activation for view fetcher. Always remember to
-        /// call this method if you are using ReactiveUI in your application.
+        /// scheduler, an activation for view fetcher, a template binding hook. Remember
+        /// to call this method if you are using ReactiveUI in your application.
         /// </summary>
         public static TAppBuilder UseReactiveUI<TAppBuilder>(this TAppBuilder builder)
-            where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
-        {
-            return builder.AfterPlatformServicesSetup(_ =>
+            where TAppBuilder : AppBuilderBase<TAppBuilder>, new() =>
+            builder.AfterPlatformServicesSetup(_ => Locator.RegisterResolverCallbackChanged(() =>
             {
+                if (Locator.CurrentMutable is null)
+                {
+                    return;
+                }
+
                 PlatformRegistrationManager.SetRegistrationNamespaces(RegistrationNamespace.Avalonia);
                 RxApp.MainThreadScheduler = AvaloniaScheduler.Instance;
                 Locator.CurrentMutable.RegisterConstant(new AvaloniaActivationForViewFetcher(), typeof(IActivationForViewFetcher));
                 Locator.CurrentMutable.RegisterConstant(new AutoDataTemplateBindingHook(), typeof(IPropertyBindingHook));
-            });
-        }
+            }));
     }
 }