Should check if URL is routed before calling getRouteName

Problem/Motivation

I want to redirect to a PDF file.

However in FieldRedirectionFormatter::shouldDeny() getRouteName() is called on the $redirect_url resulting in an UnexpectedValueException.

Steps to reproduce

Try to redirect to a pdf.

Proposed resolution

Only call getRouteName if url is routed. E.g.

$route_name = $redirect_url->isRouted() ? $redirect_url->getRouteName() : NULL;