#vulnerable code 
                                @Override
    protected Object getFallback() {
        events.add(SofaAsyncHystrixEvent.FALLBACK_EMIT);
        if (lock.getCount() > 0) {
            // > 0 说明 run 方法没有执行，或是执行时立刻失败了
            this.sofaResponse = buildEmptyResponse(request);
            lock.countDown();
            events.add(SofaAsyncHystrixEvent.FALLBACK_UNLOCKED);
        }
        FallbackFactory fallbackFactory = SofaHystrixConfig.loadFallbackFactory((ConsumerConfig) invoker.getConfig());
        if (fallbackFactory == null) {
            return super.getFallback();
        }
        Object fallback = fallbackFactory.create(null, this.getExecutionException());
        if (fallback == null) {
            return super.getFallback();
        }
        try {
            return request.getMethod().invoke(fallback, request.getMethodArgs());
        } catch (IllegalAccessException e) {
            throw new SofaRpcRuntimeException("Hystrix fallback method failed to execute.", e);
        } catch (InvocationTargetException e) {
            throw new SofaRpcRuntimeException("Hystrix fallback method failed to execute.",
                e.getTargetException());
        } finally {
            events.add(SofaAsyncHystrixEvent.FALLBACK_SUCCESS);
        }
    } 
                            #location 19 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    protected Object getFallback() {
        events.add(SofaAsyncHystrixEvent.FALLBACK_EMIT);
        if (lock.getCount() > 0) {
            // > 0 说明 run 方法没有执行，或是执行时立刻失败了
            this.sofaResponse = buildEmptyResponse(request);
            lock.countDown();
            events.add(SofaAsyncHystrixEvent.FALLBACK_UNLOCKED);
        }
        FallbackFactory fallbackFactory = SofaHystrixConfig.loadFallbackFactory((ConsumerConfig) invoker.getConfig());
        if (fallbackFactory == null) {
            return super.getFallback();
        }
        Object fallback = fallbackFactory.create(new FallbackContext(invoker, request, this.sofaResponse, this
            .getExecutionException()));
        if (fallback == null) {
            return super.getFallback();
        }
        try {
            return request.getMethod().invoke(fallback, request.getMethodArgs());
        } catch (IllegalAccessException e) {
            throw new SofaRpcRuntimeException("Hystrix fallback method failed to execute.", e);
        } catch (InvocationTargetException e) {
            throw new SofaRpcRuntimeException("Hystrix fallback method failed to execute.",
                e.getTargetException());
        } finally {
            events.add(SofaAsyncHystrixEvent.FALLBACK_SUCCESS);
        }
    }