From c7876d648c951afc33ec5ef9f91a6970f1fdc8ad Mon Sep 17 00:00:00 2001
From: themode <themode@outlook.fr>
Date: Fri, 18 Dec 2020 04:05:29 +0100
Subject: [PATCH] Fix NPE when clicking outside of the inventory to drop

---
 .../java/net/minestom/server/inventory/Inventory.java     | 7 ++++---
 .../net/minestom/server/inventory/PlayerInventory.java    | 5 +++--
 .../server/inventory/click/InventoryClickProcessor.java   | 8 ++++----
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/main/java/net/minestom/server/inventory/Inventory.java b/src/main/java/net/minestom/server/inventory/Inventory.java
index 9390ce1ba..8e9e6d95a 100644
--- a/src/main/java/net/minestom/server/inventory/Inventory.java
+++ b/src/main/java/net/minestom/server/inventory/Inventory.java
@@ -534,8 +534,9 @@ public class Inventory implements InventoryModifier, InventoryClickHandler, View
     public boolean drop(@NotNull Player player, int mode, int slot, int button) {
         final PlayerInventory playerInventory = player.getInventory();
         final boolean isInWindow = isClickInWindow(slot);
-        final ItemStack clicked = slot == -999 ?
-                null : (isInWindow ? getItemStack(slot) : playerInventory.getItemStack(slot, offset));
+        final boolean outsideDrop = slot == -999;
+        final ItemStack clicked = outsideDrop ?
+                ItemStack.getAirItem() : (isInWindow ? getItemStack(slot) : playerInventory.getItemStack(slot, offset));
         final ItemStack cursor = getCursorItem(player);
 
         final InventoryClickResult clickResult = clickProcessor.drop(this, player,
@@ -546,7 +547,7 @@ public class Inventory implements InventoryModifier, InventoryClickHandler, View
         }
 
         ItemStack resultClicked = clickResult.getClicked();
-        if (isInWindow) {
+        if (isInWindow && !outsideDrop) {
             if (resultClicked != null)
                 setItemStack(slot, resultClicked);
         } else {
diff --git a/src/main/java/net/minestom/server/inventory/PlayerInventory.java b/src/main/java/net/minestom/server/inventory/PlayerInventory.java
index 0d36098d9..33b5916d4 100644
--- a/src/main/java/net/minestom/server/inventory/PlayerInventory.java
+++ b/src/main/java/net/minestom/server/inventory/PlayerInventory.java
@@ -414,7 +414,8 @@ public class PlayerInventory implements InventoryModifier, InventoryClickHandler
     @Override
     public boolean drop(@NotNull Player player, int mode, int slot, int button) {
         final ItemStack cursor = getCursorItem();
-        final ItemStack clicked = slot == -999 ? null : getItemStack(slot, OFFSET);
+        final boolean outsideDrop = slot == -999;
+        final ItemStack clicked = outsideDrop ? ItemStack.getAirItem() : getItemStack(slot, OFFSET);
 
         final InventoryClickResult clickResult = clickProcessor.drop(null, player,
                 mode, slot, button, clicked, cursor);
@@ -423,7 +424,7 @@ public class PlayerInventory implements InventoryModifier, InventoryClickHandler
             sendSlotRefresh((short) slot, clicked);
 
         ItemStack resultClicked = clickResult.getClicked();
-        if (resultClicked != null)
+        if (resultClicked != null && !outsideDrop)
             setItemStack(slot, OFFSET, resultClicked);
         setCursorItem(clickResult.getCursor());
 
diff --git a/src/main/java/net/minestom/server/inventory/click/InventoryClickProcessor.java b/src/main/java/net/minestom/server/inventory/click/InventoryClickProcessor.java
index c6b2eb5f5..1490ddc19 100644
--- a/src/main/java/net/minestom/server/inventory/click/InventoryClickProcessor.java
+++ b/src/main/java/net/minestom/server/inventory/click/InventoryClickProcessor.java
@@ -425,17 +425,17 @@ public class InventoryClickProcessor {
 
     public InventoryClickResult drop(Inventory inventory, Player player,
                                      int mode, int slot, int button,
-                                     ItemStack clicked, ItemStack cursor) {
+                                     @NotNull ItemStack clicked, @NotNull ItemStack cursor) {
         final InventoryClickResult clickResult = startCondition(inventory, player, slot, ClickType.DROP, clicked, cursor);
 
         if (clickResult.isCancel()) {
             return clickResult;
         }
 
-        final StackingRule clickedRule = clicked == null ? null : clicked.getStackingRule();
+        final StackingRule clickedRule = clicked.getStackingRule();
         final StackingRule cursorRule = cursor.getStackingRule();
 
-        ItemStack resultClicked = clicked == null ? null : clicked.clone();
+        ItemStack resultClicked = clicked.clone();
         ItemStack resultCursor = cursor.clone();
 
 
@@ -494,7 +494,7 @@ public class InventoryClickProcessor {
     @NotNull
     private InventoryClickResult startCondition(@NotNull InventoryClickResult clickResult, @Nullable Inventory inventory,
                                                 @NotNull Player player, int slot, @NotNull ClickType clickType,
-                                                ItemStack clicked, ItemStack cursor) {
+                                                @NotNull ItemStack clicked, ItemStack cursor) {
         boolean isPlayerInventory = inventory == null;
         final int inventorySlot = isPlayerInventory ? 0 : inventory.getSize();
         isPlayerInventory = isPlayerInventory ? isPlayerInventory : slot >= inventorySlot;