ActionView::Template::Error: Validation failed: Visibility level private is not allowed since there are sub-groups with higher...

https://sentry.gitlap.com/gitlab/gitlabcom/issues/225350/

ActiveRecord::RecordInvalid: Validation failed: Visibility level private is not allowed since there are sub-groups with higher visibility.
  active_record/validations.rb:79:in `raise_record_invalid'
    raise(RecordInvalid.new(self))
  active_record/validations.rb:43:in `save!'
    perform_validations(options) ? super : raise_record_invalid
  active_record/attribute_methods/dirty.rb:29:in `save!'
    super.tap do
  active_record/transactions.rb:291:in `block in save!'
    with_transaction_returning_status { super }
  active_record/transactions.rb:351:in `block in with_transaction_returning_status'
    status = yield
...
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ActionView::Template::Error: Validation failed: Visibility level private is not allowed since there are sub-groups with higher visibility.

ActionView::Template::Error: Validation failed: Visibility level private is not allowed since there are sub-groups with higher visibility.

User reported a 422 error when accessing their group's settings/ci_cd. This seems to be caused by a public subgroup in a group that's otherwise private.

ZD: https://gitlab.zendesk.com/agent/tickets/98449 (internal)

/cc @stanhu