Add virtual room link to AK detail page

• First part of #89 (closed)
• Also fix #87 (closed)

AKPlan/templates/AKPlan/plan_akslot.html

@@ -53,7 +53,7 @@
                                 'title': '{{ slot.room }}',
                                 'start': '{{ slot.start | timezone:ak.event.timezone | date:"Y-m-d H:i:s" }}',
                                 'end': '{{ slot.end | timezone:ak.event.timezone | date:"Y-m-d H:i:s" }}',
-                                'url' : '{% url "plan:plan_room" event_slug=ak.event.slug pk=slot.room.pk %}'
+                                'url' : '{% if slot.room %}{% url "plan:plan_room" event_slug=ak.event.slug pk=slot.room.pk %}{% else %}#{% endif %}'
                             },
                         {% endif %}
                     {% endfor %}