MC-111699: Ignore Improper Anvil Item Name Packets

The client is improperly sending Item Name Packets to the server BEFORE
the click event. This causes the server to reset before the click event is processed

This breaks the ability to rename more than 1 item at a time.

See: https://bugs.mojang.com/browse/MC-111699

Spigot-Server-Patches/MC-111699-Ignore-Improper-Anvil-Item-Name-Packets.patch

@@ -0,0 +1,26 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Mon, 2 Jan 2017 02:07:24 -0500
+Subject: [PATCH] MC-111699: Ignore Improper Anvil Item Name Packets
+
+The client is improperly sending Item Name Packets to the server BEFORE
+the click event. This causes the server to reset before the click event is processed
+
+This breaks the ability to rename more than 1 item at a time.
+
+See: https://bugs.mojang.com/browse/MC-111699
+
+diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
+index 9f721d88c..3730af8df 100644
+--- a/src/main/java/net/minecraft/server/PlayerConnection.java
++++ b/src/main/java/net/minecraft/server/PlayerConnection.java
+@@ -0,0 +0,0 @@ public class PlayerConnection implements PacketListenerPlayIn, ITickable {
+                                 String s4 = SharedConstants.a(packetplayincustompayload.b().e(32767));
+ 
+                                 if (s4.length() <= 30) {
+-                                    containeranvil.a(s4);
++                                    if (!s4.isEmpty() || containeranvil.getSlot(2).getItem().isEmpty()) containeranvil.a(s4); // Paper - Hack Fix for MC-111699
+                                 }
+                             } else {
+                                 containeranvil.a("");
+--