danbarber.me/_includes/post/categories.html

{% capture category %}{% if post %}{{ post.categories | category_list | size }}{% else %}{{ page.categories | category_list | size }}{% endif %}{% endcapture %}
{% unless category == '0' %}
<span class="categories">
  {% if post %}
    {{ post.categories | category_list }}
  {% else %}
    {{ page.categories | category_list }}
  {% endif %}
</span>
{% endunless %}