Links from local user mentions on subwikis do not point to correct user profile pages

STEPS TO REPRODUCE

1. Create a subwiki
2. Create some local users on it (e.g. UL1 and UL2)
3. Login as Admin
4. On subwiki, edit a page in WYSIWYG mode
5. Type '@' and select a local user
6. Save the page
7. Click on the user profile link from the user mention macro

EXPECTED RESULTS

The link from the user mention points to the corresponding local user profile page on the subwiki.

ACTUAL RESULTS

The link points to a non existing page, on Main Wiki.