Return None for schoolterms for anonymous users

aleksis/core/schema/__init__.py

@@ -266,7 +266,7 @@ class Query(graphene.ObjectType):
     @staticmethod
     def resolve_current_school_term(root, info, **kwargs):
         if not has_person(info.context.user):
-            raise PermissionDenied
+            return None
 
         return SchoolTerm.current