#vulnerable code 
                                @Override
    public void onEvent(BlockEvent event, String fromId) {
        Block block = event.getEventBody();
        if (null == block) {
            Log.warn("recieved a null blockEvent form " + fromId);
            return;
        }
        //BlockLog.debug("download("+fromId+") block height:" + block.getHeader().getHeight() + ", preHash:" + block.getHeader().getPreHash() + " , hash:" + block.getHeader().getHash() + ", address:" + block.getHeader().getPackingAddress());
//        if (BlockBatchDownloadUtils.getInstance().downloadedBlock(fromId, block)) {
//            return;
//        }

        //blockCacheManager.addBlock(block, true, fromId);
        for (Transaction tx : block.getTxs()) {
            Transaction cachedTx = ConfirmingTxCacheManager.getInstance().getTx(tx.getHash());
            if (null == cachedTx) {
                cachedTx = ReceivedTxCacheManager.getInstance().getTx(tx.getHash());
            }
            if (null == cachedTx) {
                cachedTx = OrphanTxCacheManager.getInstance().getTx(tx.getHash());
            }
            if (cachedTx != null && cachedTx.getStatus() != tx.getStatus()) {
                tx.setStatus(cachedTx.getStatus());
                if(!(tx instanceof AbstractCoinTransaction)){
                    continue;
                }
                AbstractCoinTransaction coinTx = (AbstractCoinTransaction) tx;
                AbstractCoinTransaction cachedCoinTx = (AbstractCoinTransaction) cachedTx;
                coinTx.setCoinData(cachedCoinTx.getCoinData());
//                Log.error("the transaction status is wrong!");
            }
        }
        DownloadCacheHandler.receiveBlock(block);

    } 
                            #location 17 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public void onEvent(BlockEvent event, String fromId) {
        Block block = event.getEventBody();
        if (null == block) {
            Log.warn("recieved a null blockEvent form " + fromId);
            return;
        }

        for (Transaction tx : block.getTxs()) {
            Transaction cachedTx = txCacheManager.getTx(tx.getHash());
            if (cachedTx != null && cachedTx.getStatus() != tx.getStatus()) {
                tx.setStatus(cachedTx.getStatus());
                if (!(tx instanceof AbstractCoinTransaction)) {
                    continue;
                }
                AbstractCoinTransaction coinTx = (AbstractCoinTransaction) tx;
                AbstractCoinTransaction cachedCoinTx = (AbstractCoinTransaction) cachedTx;
                coinTx.setCoinData(cachedCoinTx.getCoinData());
//                Log.error("the transaction status is wrong!");
            }
        }
        DownloadCacheHandler.receiveBlock(block);

    }