don't let opening hours badge crash on missing data

combo_plugin_gnm/templatetags/gnm.py

@@ -44,6 +44,8 @@ class TimeSlot(object):
 
 @register.filter
 def as_opening_hours_badge(data):
+    if not data:
+        return ''
     weekdays = ['lundi', 'mardi', 'mercredi', 'jeudi', 'vendredi', 'samedi', 'dimanche']
     slots = []
     today = datetime.date.today()