#vulnerable code 
                                @Override
    public boolean removeConfig(String dataId, long timeoutMills) {
        ConfigFuture configFuture = new ConfigFuture(dataId, null, ConfigOperation.REMOVE, timeoutMills);
        configOperateExecutor.submit(new ConfigOperateRunnable(configFuture));
        return (Boolean)configFuture.get();
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public boolean removeConfig(String dataId, long timeoutMills) {
        ConfigFuture configFuture = new ConfigFuture(dataId, null, ConfigOperation.REMOVE, timeoutMills);
        configOperateExecutor.submit(new ConfigOperateRunnable(configFuture));
        return (Boolean)configFuture.get(timeoutMills, TimeUnit.MILLISECONDS);
    }