Fixing download of files in non-public mounts

[andinger]

Currently it's not possible to download files in non-public FAL mounts.

This commit fixes the error shown above

[frans-beech-it]

Can you provide the full stacktrace? If I look at the core examples there all controller methods defined in AjaxRoutes.php have ServerRequestInterface $request, ResponseInterface $response as properties

[andinger]

[nilsmehnert]

It seems neither $request nor $response are used in the controller.
I'd suggest to change it to
public function dumpFile(ServerRequestInterface $request, ResponseInterface $response = null)
to not break the defined methods as frans-beech-it mentioned