Prevent ApplicationSetting to cache nil value
What does this MR do?
Tries to fix
ApplicationSetting violation described in https://gitlab.com/gitlab-org/gitlab-ce/issues/39275
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Tests added for this feature/bug
- Has been reviewed by Backend
- Conform by the merge request performance guides
- Conform by the style guides
- Squashed related commits together