Superadmin is locked out of subwikis with "AUTHENTICATION ACTIVE CHECK" enabled

Steps to reproduce:

1. Go to Main Wiki - Global Administration - Registration and set "AUTHENTICATION ACTIVE CHECK" to Yes
2. Create 2 subwikis (S1 and S2)
3. Go to S1 - Administration - Registration and set "AUTHENTICATION ACTIVE CHECK" to Yes
4. Stop XWiki
5. Go to xwiki.cfg and enable the superadmin user
6. Start XWiki
7. Login with superadmin
8. Navigate to the Main Wiki, S1 and S2

Expected result: As superadmin, I'm able to access all wikis

Actual result: I can access the Main Wiki and S2, but I get a notice on S1.