This code may cause NPE

[Phipray]

Originally posted by @chenqiuxia in #531 (comment)

[Phipray]

Packet packet = new Packet(PacketType.MESSAGE); **packet.setSubType(PacketType.DISCONNECT);** packet.setData("channel will be closed");
SubType must not be null,otherwise it will cause NPE result to OOM !

[zhaolianwang]

#603