Fix villager trading demand MC-163962 (#3498)

Spigot-Server-Patches/0534-Fix-villager-trading-demand-MC-163962.patch

@@ -0,0 +1,20 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: chickeneer <emcchickeneer@gmail.com>
+Date: Fri, 5 Jun 2020 20:02:04 -0500
+Subject: [PATCH] Fix villager trading demand - MC-163962
+
+Prevent demand from going negative and tending to negative infinity
+
+diff --git a/src/main/java/net/minecraft/server/MerchantRecipe.java b/src/main/java/net/minecraft/server/MerchantRecipe.java
+index f1f49c2ebff93ce3537bd4a58916d4c624a3fe82..7c4dc1143696320c8b8dc21ea4ae0600d5686d62 100644
+--- a/src/main/java/net/minecraft/server/MerchantRecipe.java
++++ b/src/main/java/net/minecraft/server/MerchantRecipe.java
+@@ -104,7 +104,7 @@ public class MerchantRecipe {
+     }
+ 
+     public void e() {
+-        this.demand = this.demand + this.uses - (this.maxUses - this.uses);
++        this.demand = Math.max(0, this.demand + this.uses - (this.maxUses - this.uses)); // Paper
+     }
+ 
+     public ItemStack f() {