TMSS-745: fix bug in project-permission check when user has not project roles

SAS/TMSS/backend/src/tmss/tmssapp/viewsets/permissions.py

@@ -34,8 +34,8 @@ def get_project_roles_for_user(user):
 
         try:
             return tuple(user.project_roles)
-        except AttributeError:
-            # the user is a non-TMSSUser, for example anonyous/not-logged-in
+        except (AttributeError, TypeError):
+            # the user is a non-TMSSUser, for example anonyous/not-logged-in, or project roles are None
             # return empty project roles
             return tuple()