Landing Page preview doesn't work when content.tree_root configuration is used for the non-admin siteaccess.

After navigating to Landing Page that is a part of the configured tree and after clicking "Page" tab in the Admin UI, the 404 error is returned instead of the preview.

The displayed error (in dev mode):

No route found for "GET /site/New-tree-root" (from "http://your-site.example/admin/page/58/eng-GB")

Also, at the bottom the following error is displayed:

Cannot get page information from the server

Additionally, the following errors can be found in the browser's console:

GET http://ezplatform2-ee.local/site/New-tree-root 404 (Not Found)
GET http://ezplatform2-ee.local/studio/urlaliasinfo?url=%2FNew-tree-root&siteAccessName=site 404 (Not Found)

The issue doesn't happen in eZ Platform v1.

Steps to reproduce

1. Create a new eZ Platform v2 installation.
2. Under "Home", create new Landing Page Content Object named "New tree root". Write down its Location Id.
3. Add the following configuration to your ezplatform.yml file (using Location ID from the previous step):

       system:
           site_group:
               content:
                   tree_root:
                       location_id: 58
   

4. In Admin UI, navigate to "New tree root". Click on "Page" tab.
5. The errors described above will be shown.
   The issue also happens for Landing Pages that are descendants of the Tree Root.