[DS-121] There is gap below the menu section

[andreyzb]

Related Issue/Ticket: There is gap below the menu section

DS-121

Steps to test:

• [ ] See description for the ticket

Quality checks:

Please check these boxes to confirm this PR covers the following cases:

• Maintaining our upgrade path is essential. Check one or the other:
  • [ ] This PR provides updates via hook_update_N or other means.
  • [x] No updates are necessary for this change.
• Front end fixes should be tested against all of the Open Y Themes.
  • [x] Tested against Carnation
  • [ ] Tested against Lily
  • [ ] Tested against Rose
  • [ ] This change does not contain front-end fixes.
• [x] I have flagged this PR "Needs Review" or pinged the VY devs/QA team in Slack

[andreyzb]

Issue appears when Site search was not enabled on for the Virtual Y installation, then there is no Search button in the top menu. Search button added extra height to the menu, and when it is missing we can see the gap described in the ticket.