Remove unnecesary conversion

Also do not rely on falsiness; the first_last format is 0 and thus
falsy. It's not a problem here because that's also the default, but this
is a pure coincidence...

indico/modules/events/fields.py

@@ -117,8 +117,8 @@ def name_format(self):
         from indico.modules.users.models.users import NameFormat
         name_format = layout_settings.get(self.event, 'name_format') if self.event else None
         if name_format is None and session.user:
-            name_format = NameFormat(session.user.settings.get('name_format'))
-        return name_format or NameFormat.first_last
+            name_format = session.user.settings.get('name_format')
+        return name_format if name_format is not None else NameFormat.first_last
 
     @property
     def validate_email_url(self):