Hide filter dropdowns in plan if there are no rooms or tracks

AKPlan/templates/AKPlan/plan_index.html

@@ -76,6 +76,7 @@
 {% block content %}
     <div class="float-right">
         <ul class="nav nav-pills">
+            {% if event.room_set.count > 0 %}
                 <li class="nav-item dropdown">
                     <a class="nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button" aria-haspopup="true"
                        aria-expanded="false">{% trans "Rooms" %}</a>
@@ -86,6 +87,8 @@
                         {% endfor %}
                     </div>
                 </li>
+            {% endif %}
+            {% if event.aktrack_set.count > 0 %}
                 <li class="nav-item dropdown">
                     <a class="nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button" aria-haspopup="true"
                        aria-expanded="false">{% trans "Tracks" %}</a>
@@ -96,6 +99,7 @@
                         {% endfor %}
                     </div>
                 </li>
+            {% endif %}
             {% if event.active %}
                 <li class="nav-item">
                     <a class="nav-link active"