Don't allow sendPacket once disconnect has been processed.

CraftBukkit-Patches/0157-Clear-Packet-Queue-on-Disconnect.patch

@@ -1,4 +1,4 @@
-From edea113458ab413ab9c43ec7be3fa1382e45fece Mon Sep 17 00:00:00 2001
+From afb701ae339e92d7c574baec7d09a3b0affa123d Mon Sep 17 00:00:00 2001
 From: md_5 <git@md-5.net>
 Date: Wed, 22 Jul 2015 19:04:37 +1000
 Subject: [PATCH] Clear Packet Queue on Disconnect
@@ -16,6 +16,19 @@ index 247973d..9d23c6c 100644
              } else {
                  NetworkManager.g.warn("handleDisconnection() called twice");
              }
+diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
+index dce0ac4..e380774 100644
+--- a/src/main/java/net/minecraft/server/PlayerConnection.java
++++ b/src/main/java/net/minecraft/server/PlayerConnection.java
+@@ -868,7 +868,7 @@ public class PlayerConnection implements PacketListenerPlayIn, IUpdatePlayerList
+         }
+ 
+         // CraftBukkit start
+-        if (packet == null) {
++        if (packet == null || this.processedDisconnect) { // Spigot
+             return;
+         } else if (packet instanceof PacketPlayOutSpawnPosition) {
+             PacketPlayOutSpawnPosition packet6 = (PacketPlayOutSpawnPosition) packet;
 -- 
 2.1.4