When rendering outside a route context (drush?) there's an info on undefined routes.

Problem/Motivation

I'm seeing the following issue on a data process:

[info] preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated CssFormatter.php:192

Proposed resolution

I think it would be a good thing to do some defensive programming around that process and check if there's a current route name before looping.