#vulnerable code 
                                @Override
    public void start() {
        consensusManager.init();
        NulsContext.getInstance().setBestBlock(NulsContext.getServiceBean(BlockService.class).getLocalBestBlock());
        this.registerHandlers();
        this.consensusManager.startMaintenanceWork();
        consensusManager.joinConsensusMeeting();
        consensusManager.startPersistenceWork();

        Log.info("the POC consensus module is started!");
        TaskManager.createAndRunThread(this.getModuleId(),"block-cache-check",new BlockCacheCheckThread());
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public void start() {
        consensusManager.init();
        this.registerHandlers();
        this.consensusManager.startMaintenanceWork();
        consensusManager.joinConsensusMeeting();
        consensusManager.startPersistenceWork();

        Log.info("the POC consensus module is started!");
        TaskManager.createAndRunThread(this.getModuleId(),"block-cache-check",new BlockCacheCheckThread());
    }