Steps to reproduce

1.  Add to your light module attached test site definition test.yaml (based on travel site with es language added)
2.  Create page called "test" in pages app
3. Edit the page and see LocaleSelector - es language isn't visible there
4. By debug I found out that this is caused by the fact that instead of correct site definition (test in our case) the "fallback" site is used

Expected results

In page editor correct site definition is resolved for page.

Actual results

Fallback site is used instead of the correct one in pages editor.

Development notes

Even the restart of instance doesn't help and fallback site is still resolved. This works correctly in M6.2.x. So I would expect that this is caused by some changes in site resolving mechanism or by cahngeing the site definitions to registry.

Correct site is resolved when visiting page directly (without page editor). This can be checked by url "http://localhost:8080/magnoliaAuthor/test/es"