It's uncommon, but sometimes exceptions don't contain any error message. For example, with this route definition:

my_route:
    path: '...'
    defaults: { _controller: FrameworkBundle:Redirect:redirect, route: '', permanent: true }

When the route is empty, the RedirectController throws this exception:

        if ('' == $route) {
            throw new HttpException($permanent ? 410 : 404);
        }

Which looks like this in the browser:

What do you think if we hide the message section when it's empty? Something like this: