Poprawa błedu

Jak zrobić to by nie wywalało błędu ?

Error executing task
java.util.concurrent.ExecutionException: java.lang.AssertionError: TRAP
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:?]
at java.util.concurrent.FutureTask.get(FutureTask.java:191) ~[?:?]
at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:47) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:850) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:423) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:774) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:666) ~[patched_1.12.2.jar:git-Paper-1613]
at java.lang.Thread.run(Thread.java:835) [?:?]
Caused by: java.lang.AssertionError: TRAP
at net.minecraft.server.v1_12_R1.ItemStack.F(ItemStack.java:117) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.ItemStack.setCount(ItemStack.java:892) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.PlayerInteractManager.a(PlayerInteractManager.java:441) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1050) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.PacketPlayInBlockPlace.a(PacketPlayInBlockPlace.java:26) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.PacketPlayInBlockPlace.a(PacketPlayInBlockPlace.java:5) ~[patched_1.12.2.jar:git-Paper-1613]
at net.minecraft.server.v1_12_R1.PlayerConnectionUtils.lambda$ensureMainThread$0(PlayerConnectionUtils.java:14) ~[patched_1.12.2.jar:git-Paper-1613]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) ~[?:?]
at java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[?:?]
at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:46) ~[patched_1.12.2.jar:git-Paper-1613]

kod:

on rightclick:
	if player's tool is paper named "&5&lPotka na fly":
		remove 1 paper named "&5&lPotka na fly" from player
		execute console command "/fly %player%"
		wait 10 minutes
		execute console command "/fly %player%"
		stop