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[20:32:31] [Server thread/ERROR]: Could not pass event EntityPickupItemEvent to ItemTest v0.0.0
org.bukkit.event.EventException: null
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:319) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:589) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:576) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.EntityItem.pickup(EntityItem.java:348) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.EntityHuman.c(EntityHuman.java:458) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.EntityHuman.movementTick(EntityHuman.java:428) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.EntityLiving.tick(EntityLiving.java:2387) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.EntityHuman.tick(EntityHuman.java:153) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.EntityPlayer.playerTick(EntityPlayer.java:442) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.PlayerConnection.tick(PlayerConnection.java:143) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.NetworkManager.a(NetworkManager.java:223) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.ServerConnection.c(ServerConnection.java:128) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.MinecraftServer.b(MinecraftServer.java:1128) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.DedicatedServer.b(DedicatedServer.java:354) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.MinecraftServer.a(MinecraftServer.java:1009) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.MinecraftServer.v(MinecraftServer.java:848) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.MinecraftServer.lambda$0(MinecraftServer.java:164) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at java.lang.Thread.run(Thread.java:832) [?:?]
Caused by: java.lang.IllegalArgumentException: Cannot drop air
	at com.google.common.base.Preconditions.checkArgument(Preconditions.java:122) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at net.minecraft.server.v1_16_R1.EntityItem.setItemStack(EntityItem.java:407) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at org.bukkit.craftbukkit.v1_16_R1.entity.CraftItem.setItemStack(CraftItem.java:30) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	at com.github.stefvanschiedev.invframework.test.Main.onEntityPickupItem(Main.java:18) ~[?:?]
	at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
	at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:?]
	at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
	at java.lang.reflect.Method.invoke(Method.java:564) ~[?:?]
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:315) ~[spigot-1.16.1.jar:git-Spigot-6f4ff1b-983305b]
	... 18 more