Logout in cas mode make a redirection error

Description

When we click on logout in CAS we are not forwark to the cas portail again

Distribution Name and Version

Debian Buster

FusionDirectory Version

1.4

PHP version used

7

Origin of php packages

Debian repo

Steps to Reproduce

1. Enable CAS
2. Connect with CAS
3. Logout through CAS
4. The URL look like "http://fd.example.com/index.php?signout=1&ticket=ST-6fd6710d15749e5d7f51e9813043d718" but the browser said it's miss redirect

Maybe https://apereo.github.io/cas/4.2.x/installation/Logout-Single-Signout.html can help.

Expected behavior:

Redirect on CAS portail URL (auth.example.com in my case)

Actual behavior:

Redirect error by the browser

Reproduces how often: 100%