phpCAS: session_set_save_handler(): Cannot change save handler when session is active

public function __construct(
...
        \SessionHandlerInterface $sessionHandler = null
    ) {
...
        if (empty($sessionHandler)) {
            $sessionHandler = new CAS_Session_PhpSession;
        }
...
        $this->setSessionHandler($sessionHandler);

this calls session_set_save_handler and that won’t work if the session is allready startet. Simple workaround would be:

public function __construct(
...
        \SessionHandlerInterface $sessionHandler = null
    ) {
...
        if (!empty($sessionHandler)) {
            $this->setSessionHandler($sessionHandler);
        }
...

Greetings Frank