From 1c116bb13c7354dfa418610c1359918292e61ded Mon Sep 17 00:00:00 2001
From: Bukkit/Spigot <noreply+git-bukkit@papermc.io>
Date: Sun, 30 Dec 2018 22:27:16 +1100
Subject: [PATCH] Ignore spurious slot IDs sent by client, e.g. in enchanting
 tables

By: md_5 <git@md-5.net>
---
 .../src/main/java/org/bukkit/inventory/InventoryView.java     | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/paper-api/src/main/java/org/bukkit/inventory/InventoryView.java b/paper-api/src/main/java/org/bukkit/inventory/InventoryView.java
index 84d476a732..e13e3e3385 100644
--- a/paper-api/src/main/java/org/bukkit/inventory/InventoryView.java
+++ b/paper-api/src/main/java/org/bukkit/inventory/InventoryView.java
@@ -210,7 +210,9 @@ public abstract class InventoryView {
      * @return corresponding inventory, or null
      */
     public final Inventory getInventory(int rawSlot) {
-        if (rawSlot == OUTSIDE) {
+        // Slot may be -1 if not properly detected due to client bug
+        // e.g. dropping an item into part of the enchantment list section of an enchanting table
+        if (rawSlot == OUTSIDE || rawSlot == -1) {
             return null;
         }
         Preconditions.checkArgument(rawSlot >= 0, "Negative, non outside slot %s", rawSlot);