No need to check petitions if we are anonymous

petition/context.py

@@ -1,6 +1,8 @@
 import models
 
 def open_petitions(request):
+    if not request.user.is_authenticated():
+        return {}
     if request.user.is_staff or request.user.is_admin:
         petitions = models.Petition.objects.filter(closed=False)
     else: