Applying /disguise <entity> as player repeatedly can result in client side errors and invisible mobs

[James103]

When you run /disguise <entity> as player (or variants thereof) multiple times, you will eventually get the following error:

[15:12:47] [Render thread/FATAL]: Error executing task on Client

java.lang.NullPointerException: Cannot invoke "net.minecraft.class_640.method_2966()" because the return value of "net.minecraft.class_634.method_2871(java.util.UUID)" is null
	at Not Enough Crashes deobfuscated stack trace.(1.17.1+build.37) ~[?:?]
	at net.minecraft.client.network.ClientPlayNetworkHandler.onPlayerSpawn(ClientPlayNetworkHandler:472) ~[?:?]
	at net.minecraft.network.packet.s2c.play.PlayerSpawnS2CPacket.apply(PlayerSpawnS2CPacket:52) ~[?:?]
	at net.minecraft.network.packet.s2c.play.PlayerSpawnS2CPacket.apply(PlayerSpawnS2CPacket:10) ~[?:?]
	at net.minecraft.network.NetworkThreadUtils.method_11072(NetworkThreadUtils:21) ~[?:?]
	at net.minecraft.class_2600$$Lambda$6797/0x0000000028823158.run(Unknown Source) ~[?:?]
	at net.minecraft.util.thread.ThreadExecutor.executeTask(ThreadExecutor:151) ~[?:?]
	at net.minecraft.util.thread.ReentrantThreadExecutor.executeTask(ReentrantThreadExecutor:23) ~[?:?]
	at net.minecraft.util.thread.ThreadExecutor.runTask(ThreadExecutor:125) ~[?:?]
	at net.minecraft.util.thread.ThreadExecutor.runTasks(ThreadExecutor:110) ~[?:?]
	at net.minecraft.client.MinecraftClient.render(MinecraftClient:1075) ~[?:?]
	at net.minecraft.client.MinecraftClient.run(MinecraftClient:728) ~[?:?]
	at net.minecraft.client.main.Main.main(Main:217) [intermediary-minecraft-1.17.1-client.jar:?]
	at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
	at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[?:?]
	at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
	at java.lang.reflect.Method.invoke(Method.java:567) ~[?:?]
	at net.fabricmc.loader.game.MinecraftGameProvider.launch(MinecraftGameProvider.java:234) [fabric-loader-0.11.6.jar:?]
	at net.fabricmc.loader.launch.knot.Knot.launch(Knot.java:153) [fabric-loader-0.11.6.jar:?]
	at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:28) [fabric-loader-0.11.6.jar:?]
	at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
	at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[?:?]
	at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
	at java.lang.reflect.Method.invoke(Method.java:567) ~[?:?]
	at org.multimc.onesix.OneSixLauncher.launchWithMainClass(OneSixLauncher.java:210) [NewLaunch.jar:?]
	at org.multimc.onesix.OneSixLauncher.launch(OneSixLauncher.java:245) [NewLaunch.jar:?]
	at org.multimc.EntryPoint.listen(EntryPoint.java:143) [NewLaunch.jar:?]
	at org.multimc.EntryPoint.main(EntryPoint.java:34) [NewLaunch.jar:?]

To reproduce, first run summon pig ~ ~ ~ {CustomName:'""'}, then run the following commands in succession on repeat:

disguise @e[type=pig,limit=1,sort=nearest] as player
disguise @e[type=pig,limit=1,sort=nearest] as player 111
disguise @e[type=pig,limit=1,sort=nearest] as player 101

System Details: system.txt

[maxheyn]

I have not experienced any clientside errors but on the second disguise @e[...] as player I do get an invisible mob. Disguising it as something other than a player seems to fix it though. The skin still does not apply though, but that is another bug report.