Prevent empty items from being added to world (#7998)

The previous solution caused a bunch of bandaid fixes inorder to resolve edge cases where minecraft/the api might spawn items that are air.
Just simply prevent them from being added to the world instead.

patches/server/0915-Prevent-empty-items-from-being-added-to-world.patch

@@ -0,0 +1,33 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Owen1212055 <23108066+Owen1212055@users.noreply.github.com>
+Date: Wed, 15 Jun 2022 21:52:57 -0400
+Subject: [PATCH] Prevent empty items from being added to world
+
+The previous solution caused a bunch of bandaid fixes inorder to resolve edge cases where minecraft/the api might spawn items that are air.
+Just simply prevent them from being added to the world instead.
+
+diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
+index 0dc7a827aeacc7fae53b1f975f45883da7db6a0c..6ef4160cb9cc836371a03451bdc3f88c84167ec4 100644
+--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
++++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
+@@ -1433,6 +1433,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
+             // WorldServer.LOGGER.warn("Tried to add entity {} but it was marked as removed already", EntityTypes.getKey(entity.getType())); // CraftBukkit
+             return false;
+         } else {
++            if (entity instanceof net.minecraft.world.entity.item.ItemEntity itemEntity && itemEntity.getItem().isEmpty()) return false; // Paper - Prevent empty items from being added
+             // Paper start - capture all item additions to the world
+             if (captureDrops != null && entity instanceof net.minecraft.world.entity.item.ItemEntity) {
+                 captureDrops.add((net.minecraft.world.entity.item.ItemEntity) entity);
+diff --git a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
+index ae4b251e10babb07055d031ff48ac7dd5d4be4a0..08f15739dd7e2ab80718ab8d983b483a46309deb 100644
+--- a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
++++ b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
+@@ -509,7 +509,7 @@ public class ItemEntity extends Entity {
+     }
+ 
+     public void setItem(ItemStack stack) {
+-        com.google.common.base.Preconditions.checkArgument(!stack.isEmpty(), "Cannot drop air"); // CraftBukkit
++        // com.google.common.base.Preconditions.checkArgument(!stack.isEmpty(), "Cannot drop air"); // CraftBukkit // Paper - Remove check
+         this.getEntityData().set(ItemEntity.DATA_ITEM, stack);
+         this.getEntityData().markDirty(ItemEntity.DATA_ITEM); // CraftBukkit - SPIGOT-4591, must mark dirty
+         this.despawnRate = level.paperConfig().entities.spawning.altItemDespawnRate.enabled ? level.paperConfig().entities.spawning.altItemDespawnRate.items.getOrDefault(stack.getItem(), level.spigotConfig.itemDespawnRate) : level.spigotConfig.itemDespawnRate; // Paper