minecraft plugin ReitzMMO recipe error3

[20:29:59 ERROR]: Could not pass event EntityDeathEvent to ReitzMMO v1.17
java.lang.NumberFormatException: For input string: ""
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[?:1.8.0_212]
        at java.lang.Integer.parseInt(Integer.java:592) ~[?:1.8.0_212]
        at java.lang.Integer.parseInt(Integer.java:615) ~[?:1.8.0_212]
        at com.paully104.reitzmmo.PlayerCombatRelated.PlayerDefeatsMonster.MonsterDeathCausedByPlayer(PlayerDefeatsMonster.java:81) ~[?:?]
        at com.destroystokyo.paper.event.executor.asm.generated.GeneratedEventExecutor459.execute(Unknown Source) ~[?:?]
        at org.bukkit.plugin.EventExecutor.lambda$create$1(EventExecutor.java:69) ~[patched_1.14.3.jar:git-Paper-132]
        at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:80) ~[patched_1.14.3.jar:git-Paper-132]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[patched_1.14.3.jar:git-Paper-132]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:545) ~[patched_1.14.3.jar:git-Paper-132]
        at org.bukkit.craftbukkit.v1_14_R1.event.CraftEventFactory.callEntityDeathEvent(CraftEventFactory.java:741) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.EntityLiving.d(EntityLiving.java:1416) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.EntityLiving.die(EntityLiving.java:1354) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.EntityLiving.damageEntity(EntityLiving.java:1198) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.EntityMonster.damageEntity(EntityMonster.java:56) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.EntityArrow.a(EntityArrow.java:375) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.EntityArrow.a(EntityArrow.java:287) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.EntityArrow.tick(EntityArrow.java:198) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.EntityTippedArrow.tick(EntityTippedArrow.java:87) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.WorldServer.entityJoinedWorld(WorldServer.java:580) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.World.a(World.java:935) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.WorldServer.doTick(WorldServer.java:354) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.MinecraftServer.b(MinecraftServer.java:1192) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.DedicatedServer.b(DedicatedServer.java:420) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.MinecraftServer.a(MinecraftServer.java:1064) ~[patched_1.14.3.jar:git-Paper-132]
        at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:908) ~[patched_1.14.3.jar:git-Paper-132]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]