Wiki Creation Right set to Deny cleared when page reloaded

STEPS TO REPRODUCE

1. Login as Admin
2. Go to "Administer Wiki"
3. Go to Wikis
4. Click on Creation Right
5. Deny the "Create Wiki" right for a group/user
6. Reload the page

EXPECTED RESULTS
The page is reloaded and the Deny right remains set.

ACTUAL RESULTS
The page is reloaded and the Deny right is cleared.

Dev console error screenshot also attached.