• This issue is not solved in a development build

Describe the bug
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To Reproduce
Steps to reproduce the behavior:

1. Im running a basic superior skyblock core with essentials and world gaurd, multiworld , this error appears on login when i join and it was the reason i had to tear evrything apart to find out what was wrong, It basically does not save the /diffuculty normal and defaults to peacful or something
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
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Screenshots
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Version Info
Provide your ProtocolLib install info with /protocol dump through pastebin.

Additional context
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[15:21:23 WARN]: [ProtocolLib] [Debug] Exception registering converter
java.lang.RuntimeException: Failed to find NMS class: WorldType
at ProtocolLib.jar/com.comphenix.protocol.utility.MinecraftReflection.lambda$getMinecraftClass$4(MinecraftReflection.java:1507) ~[ProtocolLib.jar:?]
at java.base/java.util.Optional.orElseThrow(Optional.java:403) ~[?:?]
at ProtocolLib.jar/com.comphenix.protocol.utility.MinecraftReflection.getMinecraftClass(MinecraftReflection.java:1507) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.utility.MinecraftReflection.getWorldTypeClass(MinecraftReflection.java:850) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.wrappers.BukkitConverters.addConverter(BukkitConverters.java:1330) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.wrappers.BukkitConverters.getConvertersForGeneric(BukkitConverters.java:1309) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.wrappers.BukkitConverters.getUnwrappers(BukkitConverters.java:1350) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.injector.PacketConstructor.(PacketConstructor.java:61) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.injector.PacketConstructor.(PacketConstructor.java:46) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.injector.BukkitUnwrapper.unwrapItem(BukkitUnwrapper.java:107) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.utility.MinecraftFields.getNetworkManager(MinecraftFields.java:32) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.injector.netty.channel.InjectionFactory.fromPlayer(InjectionFactory.java:98) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.injector.netty.manager.NetworkManagerInjector.getInjector(NetworkManagerInjector.java:57) ~[ProtocolLib.jar:?]
at ProtocolLib.jar/com.comphenix.protocol.injector.PacketFilterManager$1.handleLogin(PacketFilterManager.java:436) ~[ProtocolLib.jar:?]
at com.destroystokyo.paper.event.executor.MethodHandleEventExecutor.execute(MethodHandleEventExecutor.java:40) ~[paper-api-1.21-R0.1-SNAPSHOT.jar:?]
at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:80) ~[paper-api-1.21-R0.1-SNAPSHOT.jar:1.21-130-b1b5d4c]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[paper-api-1.21-R0.1-SNAPSHOT.jar:?]
at io.papermc.paper.plugin.manager.PaperEventManager.callEvent(PaperEventManager.java:54) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at io.papermc.paper.plugin.manager.PaperPluginManagerImpl.callEvent(PaperPluginManagerImpl.java:131) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:628) ~[paper-api-1.21-R0.1-SNAPSHOT.jar:?]
at net.minecraft.server.players.PlayerList.canPlayerLogin(PlayerList.java:754) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.server.network.ServerLoginPacketListenerImpl.verifyLoginAndFinishConnectionSetup(ServerLoginPacketListenerImpl.java:231) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.server.network.ServerLoginPacketListenerImpl.tick(ServerLoginPacketListenerImpl.java:110) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.network.Connection.tick(Connection.java:638) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.server.network.ServerConnectionListener.tick(ServerConnectionListener.java:242) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1823) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.server.dedicated.DedicatedServer.tickChildren(DedicatedServer.java:473) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1598) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1304) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:330) ~[paper-1.21.jar:1.21-130-b1b5d4c]
at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?]