#fixed code
                                @Test
    public void testDecode() throws IOException {
        Packet packet = decoder.decodePackets(Unpooled.copiedBuffer("3:::woot", CharsetUtil.UTF_8), null);
        Assert.assertEquals(PacketType.MESSAGE, packet.getType());
        Assert.assertEquals("woot", packet.getData());
    }
#vulnerable code 
                                @Test
    public void testDecode() throws IOException {
        Packet packet = decoder.decodePacket("3:::woot", null);
        Assert.assertEquals(PacketType.MESSAGE, packet.getType());
        Assert.assertEquals("woot", packet.getData());
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE