output: #fixed code
                                  protected void checkKeycloakSession(Request request, HttpFacade facade) {
          if (request.getSessionInternal(false) == null || request.getSessionInternal().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.debugf("Cleanup and expire session %s after failed refresh", catalinaSession.getId());
          catalinaSession.removeNote(KeycloakSecurityContext.class.getName());
          request.setUserPrincipal(null);
          request.setAuthType(null);
          catalinaSession.setPrincipal(null);
          catalinaSession.setAuthType(null);
          catalinaSession.expire();
      }
input: #vulnerable code 
                                  protected void checkKeycloakSession(Request request, HttpFacade facade) {
          if (request.getSessionInternal(false) == null || request.getSessionInternal().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