#3498472: Return 404 instead of 403 when incorrect image style URL is accessed.

Closes #3498472

src/Controller/ImageStyleDownloadController.php

@@ -15,6 +15,7 @@ use Symfony\Component\HttpFoundation\BinaryFileResponse;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;
 
 /**
@@ -169,7 +170,7 @@ class ImageStyleDownloadController extends FileDownloadController {
 			}
     }
     if (!$valid) {
-      throw new AccessDeniedHttpException();
+      throw new NotFoundHttpException();
     }
 
     $derivative_uri = $image_style->buildUri($image_uri);