In the sessionlist, when a talk hasn't been allocated a track it
shows up as "None" as the Python None object is translated to a
string. Override None tracks with 'General' instead to make the
sessionlist less confusing before it's complete.
</p>
{%for track,sessionlist in sessions|groupby_sort('track', 'sortkey')%}
-<h2>{{track}}</h2>
+<h2>{{track|default_if_none:'General'}}</h2>
<ul>
{%for session in sessionlist %}
<li><a href="session/{{session.id}}-{{session.title|slugify}}/">{{session.title}}</a> ({{session.speaker_list}})</li>