[charts] Fix chart building

vrobbler/templates/books/book_detail.html

@@ -41,6 +41,13 @@
     {% endif %}
     {% endfor %}
 </div>
+{% if charts %}
+<div class="row">
+    <div class="col-md">
+        <p>{% for chart in charts %}<em><a href="{{chart.chart_url}}">{{chart}}</a></em>{% if forloop.last %}{% else %} | {% endif %}{% endfor %}</p>
+    </div>
+</div>
+{% endif %}
 <div class="row">
     <div class="col-md">
         <h3>Last scrobbles</h3>