#vulnerable code 
                                @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        SocketChannel channel = (SocketChannel) ctx.channel();
        String nodeId = IpUtil.getNodeId(channel.remoteAddress());
//        Log.debug(" ---------------------- server channelRead ------------------------- " + nodeId);
        Node node = getNetworkService().getNode(nodeId);
        if (node != null && node.isAlive()) {
            ByteBuf buf = (ByteBuf) msg;
            byte[] bytes = new byte[buf.readableBytes()];
            buf.readBytes(bytes);
            buf.release();
            ByteBuffer buffer = ByteBuffer.allocate(bytes.length);
            buffer.put(bytes);
//            getNetworkService().receiveMessage(buffer, node);
        }
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        SocketChannel channel = (SocketChannel) ctx.channel();
        String nodeId = IpUtil.getNodeId(channel.remoteAddress());
//        Log.debug(" ---------------------- server channelRead ------------------------- " + nodeId);
        Node node = networkService.getNode(nodeId);
        if (node != null && node.isAlive()) {
            ByteBuf buf = (ByteBuf) msg;
            byte[] bytes = new byte[buf.readableBytes()];
            buf.readBytes(bytes);
            buf.release();
            ByteBuffer buffer = ByteBuffer.allocate(bytes.length);
            buffer.put(bytes);
//            getNetworkService().receiveMessage(buffer, node);
        }
    }