#vulnerable code 
                                @Override
    public void start() {
        this.waitForDependencyRunning(MessageBusConstant.MODULE_ID_MESSAGE_BUS);
        this.initHandlers();
        ((DownloadServiceImpl) NulsContext.getServiceBean(DownloadService.class)).start();
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public void start() {
        this.waitForDependencyRunning(MessageBusConstant.MODULE_ID_MESSAGE_BUS);
        this.waitForDependencyInited(ConsensusConstant.MODULE_ID_CONSENSUS);
        this.initHandlers();
        ((DownloadServiceImpl) NulsContext.getServiceBean(DownloadService.class)).start();
    }