#vulnerable code 
                                @Test
    public void testDecodeId() throws IOException {
        Packet packet = decoder.decodePacket("3:1::asdfasdf", null);
        Assert.assertEquals(PacketType.MESSAGE, packet.getType());
//        Assert.assertEquals(1, (long)packet.getId());
//        Assert.assertTrue(packet.getArgs().isEmpty());
//        Assert.assertTrue(packet.getAck().equals(Boolean.TRUE));
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testDecodeId() throws IOException {
        Packet packet = decoder.decodePackets(Unpooled.copiedBuffer("3:1::asdfasdf", CharsetUtil.UTF_8), null);
        Assert.assertEquals(PacketType.MESSAGE, packet.getType());
//        Assert.assertEquals(1, (long)packet.getId());
//        Assert.assertTrue(packet.getArgs().isEmpty());
//        Assert.assertTrue(packet.getAck().equals(Boolean.TRUE));
    }