Fix villager trading demand - MC-163962

Prevent demand from going negative and tending to negative infinity

paper-server/patches/sources/net/minecraft/world/item/trading/MerchantOffer.java.patch

@@ -29,6 +29,15 @@
      private MerchantOffer(ItemCost firstBuyItem, Optional<ItemCost> secondBuyItem, ItemStack sellItem, int uses, int maxUses, boolean rewardingPlayerExperience, int specialPrice, int demandBonus, float priceMultiplier, int merchantExperience) {
          this.baseCostA = firstBuyItem;
          this.costB = secondBuyItem;
+@@ -110,7 +124,7 @@
+     }
+ 
+     public void updateDemand() {
+-        this.demand = this.demand + this.uses - (this.maxUses - this.uses);
++        this.demand = Math.max(0, this.demand + this.uses - (this.maxUses - this.uses)); // Paper - Fix MC-163962
+     }
+ 
+     public ItemStack assemble() {
 @@ -185,7 +199,11 @@
          if (!this.satisfiedBy(firstBuyStack, secondBuyStack)) {
              return false;