FIX ArgumentCountError in UploadController::saveMedia

New code parameter from the commit with
SHA: be6a8cc1c1ecfe9489fb51e4869af15a13fc2cd2
needs default value to work with php 7.1+ (https://www.php.net/manual/en/migration71.incompatible.php)

app/Controllers/UploadController.php

@@ -118,7 +118,6 @@ public function uploadEndpoint(Request $request, Response $response): Response
     /**
      * @param  Request  $request
      * @param  Response  $response
-     * @param $code
      * @return UploadedFileInterface
      * @throws ValidationException
      */
@@ -179,11 +178,12 @@ protected function validateUser(Request $request, Response $response, UploadedFi
      * @param  Response  $response
      * @param  UploadedFileInterface  $file
      * @param $user
+     * @param $code
      * @return Response
      * @throws \League\Flysystem\FileExistsException
      * @throws \League\Flysystem\FileNotFoundException
      */
-    protected function saveMedia(Response $response, UploadedFileInterface $file, $user, $code)
+    protected function saveMedia(Response $response, UploadedFileInterface $file, $user, $code = null)
     {
         if ($code === null) {
             do {