[Backport 15.1] You cannot create a new variant if you are not on the component's page

You can't create a new variant and you can't save changes to the selected variant

Steps to reproduce

Scenario:

1. Go to CM
2. Click on a component, it triggers to open the right-side panel
3. Make some changes
4. In sitemap select a different page
5. In the right-side panel, click the save button

Actual behavior:
Doesn't save changes
Expected behavior:
Saves changes

Solution:
Disable the variant section on a foreign page so the user can't create a new variant or switch between them or delete a variant.