#vulnerable code 
                                protected void checkKeycloakSession(Request request, HttpFacade facade) {
        if (request.getSessionInternal(false) == null || request.getPrincipal() == null) return;
        RefreshableKeycloakSecurityContext session = (RefreshableKeycloakSecurityContext) request.getSessionInternal().getNote(KeycloakSecurityContext.class.getName());
        if (session == null) return;
        // just in case session got serialized
        if (session.getDeployment() == null) session.setDeployment(deploymentContext.resolveDeployment(facade));
        if (session.isActive() && !session.getDeployment().isAlwaysRefreshToken()) return;

        // FYI: A refresh requires same scope, so same roles will be set.  Otherwise, refresh will fail and token will
        // not be updated
        boolean success = session.refreshExpiredToken(false);
        if (success && session.isActive()) return;

        request.getSessionInternal().removeNote(KeycloakSecurityContext.class.getName());
        request.setUserPrincipal(null);
        request.setAuthType(null);
        request.getSessionInternal().setPrincipal(null);
        request.getSessionInternal().setAuthType(null);
    } 
                            #location 7 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                protected void checkKeycloakSession(Request request, HttpFacade facade) {
        if (request.getSessionInternal(false) == null || request.getPrincipal() == null) return;
        RefreshableKeycloakSecurityContext session = (RefreshableKeycloakSecurityContext) request.getSessionInternal().getNote(KeycloakSecurityContext.class.getName());
        if (session == null) return;
        // just in case session got serialized
        if (session.getDeployment() == null) session.setDeployment(deploymentContext.resolveDeployment(facade));
        if (session.isActive() && !session.getDeployment().isAlwaysRefreshToken()) return;

        // FYI: A refresh requires same scope, so same roles will be set.  Otherwise, refresh will fail and token will
        // not be updated
        boolean success = session.refreshExpiredToken(false);
        if (success && session.isActive()) return;

        // Refresh failed, so user is already logged out from keycloak. Cleanup and expire our session
        Session catalinaSession = request.getSessionInternal();
        log.fine("Cleanup and expire session " + catalinaSession + " after failed refresh");
        catalinaSession.removeNote(KeycloakSecurityContext.class.getName());
        request.setUserPrincipal(null);
        request.setAuthType(null);
        catalinaSession.setPrincipal(null);
        catalinaSession.setAuthType(null);
        catalinaSession.expire();
    }