Make blog depiction credits optional

templates/blog/card.html

@@ -3,7 +3,9 @@
               <a href="{{ post.permalink }}">
                 <figure class="image is-4by3">
                   <img src="{{ get_url(path="@/" ~ post.relative_path, trailing_slash=true) }}{{ post.extra.depiction.image | safe }}" alt="{{ post.extra.depiction.alt }}" />
-                  <figcaption>{{ post.extra.depiction.credits }}</figcaption>
+                  {% if post.extra.depiction.credits %}
+                    <figcaption>{{ post.extra.depiction.credits }}</figcaption>
+                  {% endif %}
                 </figure>
               </a>
             </div>