Thread:Extension talk:UserAdmin/? for % fix not working for No such special page

Hello, I read some past posts on this page and found the fix that switches the ? for a & in the URL, but when applying that I get the following error:

Fatal error: Wrong parameters for Exception([string $exception [, long $code ]]) in /ip/ois/www/admissions/wiki/extensions/UserAdmin/SpecialUADMBase.class.php on line 43

The URL being requested is: http://ois.indiana.edu/admissions/wiki/index.php?title=Special:AddUser&returnto=Special%3AUserAdmin

The version I'm using is 1.19.7, in case that may be a factor. Any help would be greatly appreciated.