Refactor HTML structure

_includes/disqus.html

@@ -2,6 +2,8 @@
   The Disqus lazy loading.
 -->
 
+{% if site.disqus.comments and page.comments %}
+
 <div id="disqus_thread" class="pt-2 pb-2">
   <p class="text-center text-muted small">
     Comments powered by <a href="https://disqus.com/">Disqus</a>.
@@ -52,3 +54,5 @@
   }
 
 </script>
+
+{% endif %}