Merge branch 'bugfix/NotFound' into develop

Previously, the `[ValidateTopic]` attribute returned a custom error message alongside the `NotFound` result. As a result, the `UseStatusCodePages()` middleware failed to intercept the request since it had already written to the response stream. By removing this custom message, we ensure that the `UseStatusCodePages()` middleware can take effect. This includes an integration test to confirm this fix resolves the issue.

Author: JeremyCaney

OnTopic.AspNetCore.Mvc.IntegrationTests/ServiceCollectionExtensionsTests.cs

@@ -94,6 +94,7 @@ public async Task MapTopicSitemap_RespondsToRequest() {
     /// </summary>
     [Theory]
     [InlineData("/MissingPage/", HttpStatusCode.NotFound, "400")]
+    [InlineData("/Web/MissingPage/", HttpStatusCode.NotFound, "400")]
     [InlineData("/Web/Container/", HttpStatusCode.Forbidden, "400")]
     public async Task UseStatusCodePages_ReturnsExpectedStatusCode(string path, HttpStatusCode statusCode, string expectedContent) {
 

OnTopic.AspNetCore.Mvc/_filters/ValidateTopicAttribute.cs

@@ -75,7 +75,7 @@ public override void OnActionExecuting(ActionExecutingContext context) {
 
       if (currentTopic is null) {
         if (!AllowNull) {
-          context.Result = controller.NotFound("There is no topic associated with this path.");
+          context.Result = controller.NotFound();
         }
         return;
       }