User should not be allowed to remove a locale from Portal/Company Settings being used by default in a site locale

• Type: Regression Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 7.0.X, 7.1.X, Master
• Fix Version/s: 7.0.0 DXP FP66, 7.0.X, 7.1.10 DXP FP3, 7.1.1 CE GA2, 7.1.10.1 SP1, 7.1.X, Master
• Component/s: Portal Configuration > Portal Settings, Portal Services > Localization
• Labels:
  • liferay-dxp-70-sp10
  • liferay-dxp-71-sp1
  • liferay-fixpack-de-66-7010
  • liferay-fixpack-dxp-3-7110
• Branch Version/s:
  7.1.x, 7.0.x
• Backported to Branch:
  Committed
• Fix Priority: 3
• Sprint: U&SM | Sprint 1
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/63148

Description
If we remove a locale Portal wide that is currently being used in a Site, then when navigating to certain areas in the Site, a lot of the CSS / functionality breaks. We should not allow the user to perform the action, or do something else to workaround this error from occuring.

Steps to Reproduce

1. Set a Language to be default for a Site (need to set a new one instead of inheriting from portal settings)
2. Remove the default Language for the site from Portal/Company (Instance Settings)
3. Navigate to various areas in the site that uses the missing language like in the video

Expected Result
Interaction prevented or some other error check / workaround

Actual Result
A lot of CSS classes break and functionality is affected.

Reproduced on Tomcat 9.0.6 + MariaDB 10.2
Portal 7.1.x-private GIT ID: 73d4741be42fa9386ae6861208ac50743e7026f9
git-commit-portal: fc0ac2856e26187ee77703de46e555ff63a512a4