Only display active timers nav menu if active timers exist.

core/templates/core/timer_nav.html

@@ -19,12 +19,14 @@
                 <i class="fa fa-list" aria-hidden="true"></i> View Timers
             </a>
         {% endif %}
+        {% if timers %}
             <div class="dropdown-divider"></div>
             <h6 class="dropdown-header">Active Timers</h6>
             {% for timer in timers %}
                 <a class="dropdown-item" href="{% url 'timer-detail' timer.id %}">{{ timer }} ({{ timer.user }})</a>
             {% empty %}
-            None
+                <a class="dropdown-item disabled" href="#">None</a>
             {% endfor %}
+        {% endif %}
     </div>
 </li>