On logout, PHPCas::client could be already called

[Alexandre-T]

On logout, phpCAS::client could be called two times and crash.

We shall test phpCAS::isInitialized() before.

public function onLogoutSuccess(Request $request)
{
    phpCAS::setDebug($this->cas->getDebug());
    phpCAS::setVerbose($this->cas->isVerbose());
    if (!phpCAS::isInitialized()) {
        phpCAS::client(
            $this->cas->getVersion(),
            $this->cas->getHostname(),
            $this->cas->getPort(),
            $this->cas->getUrl()
        );
    }

}