Throw 404 when blog post fails to load.

Website/Controllers/BlogController.cs

@@ -30,9 +30,13 @@ namespace Website.Controllers
 
 		public async Task<IActionResult> Entry(string url)
 		{
+			try {
 				var post = await _repo.GetPostByUrlAsync(url);
 				var model = new BlogPostViewModel(post);
 				return View(model);
+			} catch (InvalidOperationException e) {
+				return NotFound();
+			}
 		}
 	}
 }

Website/Startup.cs

@@ -47,11 +47,11 @@ namespace Website
 			else
 			{
 				app.UseExceptionHandler("/Error/ServerError");
-				app.UseStatusCodePagesWithReExecute("/Error/PageNotFound");
 				// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
 				app.UseHsts();
 			}
 
+			app.UseStatusCodePagesWithReExecute("/Error/PageNotFound");
 			app.UseHttpsRedirection();
 			app.UseStaticFiles();