Fix the error with nullable email (django.contrib.auth compat).

ssoauth/auth_utils.py

@@ -92,7 +92,7 @@ def update_user_data(user, surname=None, forename=None, email=None):
     assert isinstance(user, get_user_model())
     user.first_name = forename or str()
     user.last_name = surname or str()
-    user.email = email or None
+    user.email = email or ""
     user.save()