Fixed heading layout in blockquote.

When one post have only one category will hit the bug.

_includes/head.html

@@ -145,6 +145,8 @@
   <script src="{{ site.baseurl }}/assets/js/dist/tooltip-loader.min.js" async></script>
 
   <!-- PWA -->
-  <script src="{{ '/app.js' | relative_url }}" defer></script>
+  {% if jekyll.environment == 'production' %}
+    <script src="{{ '/app.js' | relative_url }}" defer></script>
+  {% endif %}
 
 </head>

assets/css/_addon/module.scss

@@ -49,8 +49,8 @@
 }
 
 %anchor {
-  .post-content &,
-  #page & {
+  .post-content>&,
+  #page>& {
     padding-top: 3.5rem;
     margin-top: -2.5rem;
   }

tabs/categories.md

@@ -20,9 +20,11 @@ title: Categories
 
     {% for post in posts_of_category %}
       {% assign second_category = post.categories[1] %}
-      {% unless sub_categories contains second_category %}
-        {% assign sub_categories = sub_categories | push: second_category %}
-      {% endunless %}
+      {% if second_category %}
+        {% unless sub_categories contains second_category %}
+          {% assign sub_categories = sub_categories | push: second_category %}
+        {% endunless %}
+      {% endif %}
     {% endfor %}
 
     {% assign sub_categories = sub_categories | sort %}