Fatal Error - Think the system needs an update but I can't access the backend

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Hello,

I can a fatal error when trying to go to the login page for this site:http://www.login.chaplaincyinstitute.org/login/...

Fatal error: Cannot unset $this in /home/dev24096/public_html/loginpage/updates/concrete5.6.3.2/concrete/libraries/3rdparty/adodb/adodb-xmlschema03.inc.php on line 178

Any ideas how to fix? Thanks!