QB server gives "Gitlab webhook setting not defined" and a build is not run when a configuration has a inherited GitLab webhook setting but does not override it.

Steps:
1. Setup a PARENT configuration to accept GitLab webhooks.
2. See that a CHILD configuration has the parent's GitLab webhook setting.
3. Setup a GitLab project to run webhook request to QB server for the CHILD configuration
4. Test the webhook on GitLab.
5. See that QB server responds "Gitlab webhook setting not defined" (with no error status code due to QB-3416) and no new build is run.

6. Change the setup of the CHILD configuration to override the PARENT's GitLab webhook setting (press "Override" and then "Save")
7. Repeat step 4.
8. Observe that QB runs a new build request as expected

I'm expecting that a new build is run after step 4