Moved locale middleware to before the not found handler, so that it never gets executed otherwise

config/autoload/middleware-pipeline.global.php

@@ -13,7 +13,6 @@ return [
             'middleware' => [
                 ErrorHandler::class,
                 Expressive\Helper\ContentLengthMiddleware::class,
-                Common\Middleware\LocaleMiddleware::class,
             ],
             'priority' => 12,
         ],
@@ -47,6 +46,9 @@ return [
         'post-routing' => [
             'middleware' => [
                 Expressive\Router\Middleware\DispatchMiddleware::class,
+
+                // Only if a not found error is triggered, set-up the locale to be used
+                Common\Middleware\LocaleMiddleware::class,
                 Core\Response\NotFoundHandler::class,
             ],
             'priority' => 1,

module/Core/src/Response/NotFoundHandler.php

@@ -55,6 +55,6 @@ class NotFoundHandler implements RequestHandlerInterface
         }
 
         $notFoundTemplate = $request->getAttribute(self::NOT_FOUND_TEMPLATE, $this->defaultTemplate);
-        return new Response\HtmlResponse($this->renderer->render($notFoundTemplate, ['request' => $request]), $status);
+        return new Response\HtmlResponse($this->renderer->render($notFoundTemplate), $status);
     }
 }