Page title on first install steps is broken

Because we are using raw $site_config->get('name') in template_preprocess_html(), on steps where site name is not exist we will have page title like this:

<title>Requirements problem | </title>

Meanwhile in template_preprocess_install_page() we have logic to fetch some value for.
I think about different ways of solution, but seems most clean and safe is to repeat same logic in template_preprocess_html().