Player head drops causes dupe on death on players using invalid skins

[capthehacker99]

Expected behavior

The inventory not duping

Observed/Actual behavior

The inventory duped.
Items dropped on ground while items still in inventory after respawn.
It also produced the following error in console

[00:40:58 ERROR]: Failed to handle packet net.minecraft.network.protocol.game.PacketPlayInUseEntity@7f69b4fc, suppressing error>
java.lang.NullPointerException: Cannot invoke "net.minecraft.nbt.NBTBase.d()" because the return value of "java.util.Map$Entry.getValue()" is null
	at net.minecraft.nbt.CompoundTag.copy(CompoundTag.java:473) ~[?:?]
	at net.minecraft.world.item.ItemStack.copy(ItemStack.java:733) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.world.item.ItemStack.copy(ItemStack.java:721) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.network.syncher.EntityDataSerializers$1.copy(EntityDataSerializers.java:55) ~[?:?]
	at net.minecraft.network.syncher.EntityDataSerializers$1.copy(EntityDataSerializers.java:42) ~[?:?]
	at net.minecraft.network.syncher.SynchedEntityData$DataValue.create(SynchedEntityData.java:358) ~[?:?]
	at net.minecraft.network.syncher.SynchedEntityData$DataItem.value(SynchedEntityData.java:349) ~[?:?]
	at net.minecraft.network.syncher.SynchedEntityData.getNonDefaultValues(SynchedEntityData.java:211) ~[?:?]
	at net.minecraft.server.level.ServerEntity.<init>(ServerEntity.java:90) ~[?:?]
	at net.minecraft.server.level.ChunkMap$TrackedEntity.<init>(ChunkMap.java:1437) ~[?:?]
	at net.minecraft.server.level.ChunkMap.addEntity(ChunkMap.java:1203) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.server.level.ServerChunkCache.addEntity(ServerChunkCache.java:769) ~[?:?]
	at net.minecraft.server.level.ServerLevel$EntityCallbacks.onTrackingStart(ServerLevel.java:2714) ~[?:?]
	at net.minecraft.server.level.ServerLevel$EntityCallbacks.c(ServerLevel.java:2653) ~[?:?]
	at io.papermc.paper.chunk.system.entity.EntityLookup.entityStatusChange(EntityLookup.java:271) ~[paper-1.20.1.jar:git-Paper-50]
	at io.papermc.paper.chunk.system.entity.EntityLookup.addEntity(EntityLookup.java:394) ~[paper-1.20.1.jar:git-Paper-50]
	at io.papermc.paper.chunk.system.entity.EntityLookup.addNewEntity(EntityLookup.java:332) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.server.level.ServerLevel.addEntity(ServerLevel.java:1661) ~[?:?]
	at net.minecraft.server.level.ServerLevel.addFreshEntity(ServerLevel.java:1564) ~[?:?]
	at org.bukkit.craftbukkit.v1_20_R1.CraftWorld.dropItem(CraftWorld.java:709) ~[paper-1.20.1.jar:git-Paper-50]
	at org.bukkit.craftbukkit.v1_20_R1.CraftWorld.dropItem(CraftWorld.java:695) ~[paper-1.20.1.jar:git-Paper-50]
	at org.bukkit.craftbukkit.v1_20_R1.event.CraftEventFactory.callPlayerDeathEvent(CraftEventFactory.java:939) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.server.level.ServerPlayer.die(ServerPlayer.java:958) ~[?:?]
	at net.minecraft.world.entity.LivingEntity.hurt(LivingEntity.java:1529) ~[?:?]
	at net.minecraft.world.entity.player.Player.hurt(Player.java:967) ~[?:?]
	at net.minecraft.server.level.ServerPlayer.hurt(ServerPlayer.java:1127) ~[?:?]
	at net.minecraft.world.entity.player.Player.attack(Player.java:1320) ~[?:?]
	at net.minecraft.server.level.ServerPlayer.attack(ServerPlayer.java:2162) ~[?:?]
	at net.minecraft.server.network.ServerGamePacketListenerImpl$5.a(ServerGamePacketListenerImpl.java:2875) ~[?:?]
	at net.minecraft.network.protocol.game.ServerboundInteractPacket$1.dispatch(ServerboundInteractPacket.java:24) ~[?:?]
	at net.minecraft.network.protocol.game.ServerboundInteractPacket.dispatch(ServerboundInteractPacket.java:80) ~[?:?]
	at net.minecraft.server.network.ServerGamePacketListenerImpl.handleInteract(ServerGamePacketListenerImpl.java:2799) ~[?:?]
	at net.minecraft.network.protocol.game.ServerboundInteractPacket.handle(ServerboundInteractPacket.java:67) ~[?:?]
	at net.minecraft.network.protocol.game.ServerboundInteractPacket.handle(ServerboundInteractPacket.java:12) ~[?:?]
	at net.minecraft.network.protocol.PacketUtils.lambda$ensureRunningOnSameThread$0(PacketUtils.java:51) ~[?:?]
	at net.minecraft.server.TickTask.run(TickTask.java:18) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.util.thread.BlockableEventLoop.doRunTask(BlockableEventLoop.java:153) ~[?:?]
	at net.minecraft.util.thread.ReentrantBlockableEventLoop.doRunTask(ReentrantBlockableEventLoop.java:24) ~[?:?]
	at net.minecraft.server.MinecraftServer.doRunTask(MinecraftServer.java:1339) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.server.MinecraftServer.d(MinecraftServer.java:197) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.util.thread.BlockableEventLoop.pollTask(BlockableEventLoop.java:126) ~[?:?]
	at net.minecraft.server.MinecraftServer.pollTaskInternal(MinecraftServer.java:1316) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.server.MinecraftServer.pollTask(MinecraftServer.java:1309) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.util.thread.BlockableEventLoop.managedBlock(BlockableEventLoop.java:136) ~[?:?]
	at net.minecraft.server.MinecraftServer.waitUntilNextTick(MinecraftServer.java:1287) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1175) ~[paper-1.20.1.jar:git-Paper-50]
	at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:318) ~[paper-1.20.1.jar:git-Paper-50]
	at java.lang.Thread.run(Thread.java:833) ~[?:?]

Steps/models to reproduce

Enable player head drops.
Kill player with invalid skin.

Plugin and Datapack List

Plugins:

PaperTweaks

Datapacks:

[vanilla (built-in)]
[file/bukkit (world)]

Server Version Info

This server is running Paper version git-Paper-50 (MC: 1.20.1) (Implementing API version 1.20.1-R0.1-SNAPSHOT) (Git: 990be16)
Error obtaining version information
Previous version: git-Paper-43 (MC: 1.20.1)

Plugin Version

0.3.0-SNAPSHOT

Other

The easiest way to get player with invalid skin is to set online-mode to false and make an offline player whose username doesn't exist join.
I am not endorsing pirating the game in any way. This is just the most effective way to reproduce this.

[1nfameArts]

Does it work as expected with online-mode true?