Version conflict window is displayed when editing DefaultSkin page

STEPS TO REPRODUCE

1. Login as Admin
2. Go to XWiki.DefaultSkin
3. Click 'Edit this skin'
4. On 'Overridden templates' section, click 'Add' on the existing template (e.g. file.vm) or add another .vm file
5. Type something in the 'Content' field
6. Click 'Save' or 'Save & View'

EXPECTED RESULTS

The page is saved with the respective modifications.

ACTUAL RESULTS

A version conflict window is displayed, as if the page was already saved in the meantime.

The issue could be reproduced also on XWiki 11.4.