use sanitized reference

Author: expikr

src/theme/index.hbs

@@ -59,6 +59,7 @@
         <script>
             var path_to_root = "{{ path_to_root }}";
             var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "{{ preferred_dark_theme }}" : "{{ default_theme }}";
+            default_theme = default_theme.replace(/\W+/g, '_').toLowerCase();
         </script>
 
         <!-- Work around some values being stored in localStorage wrapped in quotes -->
@@ -85,7 +86,7 @@
             var html = document.querySelector('html');
             html.classList.remove('no-js')
             try { 
-                html.classList.remove('{{ default_theme }}');
+                html.classList.remove(default_theme);
                 html.classList.add(theme.replace(/\W+/g, '_').toLowerCase()); 
             } catch(e) { }
             html.classList.add('js');