Fixes #37178 - use safe navigation for operatingsystem

[jeremylenz]

What are the changes introduced in this pull request?

Use Ruby safe navigation operator for operatingsystem. This fixes a bug introduced in #10881

Considerations taken when implementing this change?

What are the testing steps for this pull request?

Clone a registered rhel8 host
Make sure you can display the host details page without getting a 500

[ekohl]

I think unmanaged systems don't have an OS, so this is correct.

In hindsight we should have nested the whole OS as its own node, rather than a set of properties. I can see this is consistent with operatingsystem_id and operatingsystem_name`, but this would have been better IMHO:

{
  "operatingsystem": {
    "id": 1,
    "name": "",
    "family": "",
    "major": ""
  }
}

But that would mean a major redesign of the API and I don't see that happening soon.

[chris1984]

Code change looks fine and going off what Ewoud said, this looks ok. Going to start testing

[chris1984]

ACK,

Looks good, before PR:

14:02:26 rails.1   | 2024-02-27T14:02:26 [I|app|8bb69bda] Backtrace for 'Action failed' error (ActionView::Template::Error): undefined method `family' for nil:NilClass
14:02:26 rails.1   |  8bb69bda | /home/vagrant/katello/app/views/katello/api/v2/hosts/base.json.rabl:10:in `block in cached_source_4461041918095890411'

After PR:
No error

[jeremylenz]

rebased

[ianballou]

[test katello]