An invalid XWiki.XWikiRights object is created by com.xpn.xwiki.XWiki.ProtectUserPage() with a field named "levelsye" at line 1827. This field is not in the current schema, though one named "levels", which is not added to this object, is. Accordingly, it appears that the appropriate corrective action would simply be to remove the last two letters from the field name in that line - or it would be but for the corruption of the default database, version 9.2 (at least) which contains multiple instances of the resulting object.
This bug aggravates another bug -
XWIKI-342 - which causes the copying or renaming of user profile documents (those created by XWiki.createUser()) to fail silently.