Changes for case when no cards are in db

pocwww/home.py

@@ -24,10 +24,10 @@ def my_view(request):
     for t in latesttag_agg:
         latest_tag_values.append(t)
 
-    latest_card = []
+    latest_card = None
     try:
         latest_card = list(request.db['cards'].find().sort("timestamp", -1).limit(1))[0]
     except IndexError:
-        latest_card = []
+        latest_card = None
 
     return {'project': 'POC Web Interface', 'navgroup': 'dashboard', 'tag_values': latest_tag_values, 'card': latest_card}

pocwww/templates/dashboard.jinja2

@@ -57,7 +57,7 @@
         </div>
         <div class="col-md-6">
             <h2 class="allcaps">Latest Card</h2>
-            {% if card is defined %}
+            {% if card is mapping %}
             <h3>{{card.timestamp | datetime('long')}}</h1>
                 <canvas id="surfacecard" height="140"></canvas>
                 <canvas id="downholecard" height="140"></canvas>