ClassCastException when getting commands from a non-JavaPlugin plugin

[ha29mya3]

What happened:

Could not pass event PlayerCommandPreprocessEvent to GriefPrevention v16.12.0-d4d7ac4

What was expected:

nothing

Steps to reproduce:

issue a command

Server and GriefPrevention version:

This can be found by running /version and /version GriefPrevention on your server.
Paste of /version:
This server is running Paper version git-Paper-84 (MC: 1.15.2) (Implementing API version 1.15.2-R0.1-SNAPSHOT) Previous version: git-Paper-83 (MC: 1.15.2) You are running the latest version
Paste of /version GriefPrevention:
GriefPrevention version 16.12.0-d4d7ac4

Stack trace/error or server log

[10:41:27 ERROR]: Could not pass event PlayerCommandPreprocessEvent to GriefPrevention v16.12.0-d4d7ac4
java.lang.ClassCastException: nz.co.jammehcow.lukkit.environment.plugin.LukkitPlugin incompatible with org.bukkit.plugin.java.JavaPlugin
	at me.ryanhamshire.GriefPrevention.PlayerEventHandler.getCommandCategory(PlayerEventHandler.java:551) ~[?:?]
	at me.ryanhamshire.GriefPrevention.PlayerEventHandler.onPlayerCommandPreprocess(PlayerEventHandler.java:394) ~[?:?]
	at java.lang.invoke.VirtualHandle.invokeExact_thunkArchetype_V(Unknown Source) ~[?:?]
	at java.lang.invoke.AsTypeHandle.invokeExact_thunkArchetype_X(Unknown Source) ~[?:?]
	at com.destroystokyo.paper.event.executor.MethodHandleEventExecutor.execute(MethodHandleEventExecutor.java:37) ~[papermc.jar:git-Paper-84]
	at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:80) ~[papermc.jar:git-Paper-84]
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[papermc.jar:git-Paper-84]
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:561) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.PlayerConnection.handleCommand(PlayerConnection.java:1812) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.PlayerConnection.a(PlayerConnection.java:1628) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.PacketPlayInChat.a(PacketPlayInChat.java:47) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.PacketPlayInChat.a(PacketPlayInChat.java:5) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.PlayerConnectionUtils.lambda$ensureMainThread$0(PlayerConnectionUtils.java:23) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.PlayerConnectionUtils$$Lambda$3743/000000002815EF50.run(Unknown Source) ~[?:?]
	at net.minecraft.server.v1_15_R1.TickTask.run(SourceFile:18) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeTask(IAsyncTaskHandler.java:136) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.IAsyncTaskHandlerReentrant.executeTask(SourceFile:23) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeNext(IAsyncTaskHandler.java:109) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.MinecraftServer.ba(MinecraftServer.java:1038) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.MinecraftServer.executeNext(MinecraftServer.java:1031) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.awaitTasks(IAsyncTaskHandler.java:119) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.MinecraftServer.sleepForTick(MinecraftServer.java:1015) ~[papermc.jar:git-Paper-84]
	at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:938) ~[papermc.jar:git-Paper-84]
	at java.lang.Thread.run(Unknown Source) [?:?]

GriefPrevention config.yml

default

Plugin list (if applicable):

Debugging steps attempted

• I attempted running only GriefPrevention on the server
  • Issue still occurs even if GriefPrevention is the only plugin running
• I attempted testing for the issue on a new server
  • Issue still occurs even after testing on a new server

[RoboMWM]

Missing version info.

[RoboMWM]

nz.co.jammehcow.lukkit.environment.plugin.LukkitPlugin

What is this plugin and why has it registered something else in the PluginManager??? I'll add a check for this but very curious why it has something in here that doesn't extend JavaPlugin