Gracefully handle users with no ticket

pinaxcon/templatetags/lca2018_tags.py

@@ -102,6 +102,9 @@ def ticket_type(context):
     # Default to purchased ticket type (only item from category 1)
     items = registrasion_tags.items_purchased(context, 1)
 
+    if not items:
+        return "NO TICKET"
+
     item = next(iter(items))
     name = item.product.name
     if name == "Conference Volunteer":