Got following error, ideas?

`function: OnZombieDead -- file: LowQualityZombieClothing.lua line # 39 | MOD: Low Quality Zombie Clothing
java.lang.RuntimeException: __mul not defined for operands in OnZombieDead
at se.krka.kahlua.vm.KahluaUtil.fail(KahluaUtil.java:82)
at se.krka.kahlua.vm.KahluaThread.luaMainloop(KahluaThread.java:676)
at se.krka.kahlua.vm.KahluaThread.call(KahluaThread.java:163)
at se.krka.kahlua.vm.KahluaThread.pcall(KahluaThread.java:1980)
at se.krka.kahlua.vm.KahluaThread.pcallvoid(KahluaThread.java:1812)
at se.krka.kahlua.integration.LuaCaller.pcallvoid(LuaCaller.java:66)
at se.krka.kahlua.integration.LuaCaller.protectedCallVoid(LuaCaller.java:139)
at zombie.Lua.Event.trigger(Event.java:64)
at zombie.Lua.LuaEventManager.triggerEvent(LuaEventManager.java:92)
at zombie.characters.IsoZombie.Kill(IsoZombie.java:5115)
at zombie.characters.IsoZombie.Kill(IsoZombie.java:5129)
at zombie.characters.IsoGameCharacter.hitConsequences(IsoGameCharacter.java:6731)
at zombie.characters.IsoZombie.hitConsequences(IsoZombie.java:3528)
at zombie.characters.IsoGameCharacter.Hit(IsoGameCharacter.java:6537)
at zombie.characters.IsoZombie.Hit(IsoZombie.java:928)
at zombie.characters.IsoGameCharacter.Hit(IsoGameCharacter.java:6398)
at zombie.ai.states.SwipeStatePlayer.ConnectSwing(SwipeStatePlayer.java:2097)
at zombie.ai.states.SwipeStatePlayer.animEvent(SwipeStatePlayer.java:392)
at zombie.ai.StateMachine.lambda$stateAnimEvent$6(StateMachine.java:268)
at zombie.util.lambda.Consumers$Params2$CallbackStackItem.accept(Consumers.java:93)
at zombie.util.list.PZArrayUtil.forEach(PZArrayUtil.java:904)
at zombie.util.Lambda.lambda$forEachFrom$3(Lambda.java:219)
at zombie.util.lambda.Stacks$Params5$CallbackStackItem.invoke(Stacks.java:345)
at zombie.util.lambda.Stacks$GenericStack.invokeAndRelease(Stacks.java:26)
at zombie.util.Lambda.capture(Lambda.java:142)
at zombie.util.Lambda.forEachFrom(Lambda.java:216)
at zombie.ai.StateMachine.stateAnimEvent(StateMachine.java:264)
at zombie.characters.IsoGameCharacter.OnAnimEvent(IsoGameCharacter.java:4235)
at zombie.characters.IsoPlayer.OnAnimEvent(IsoPlayer.java:9401)
at zombie.core.skinnedmodel.advancedanimation.AdvancedAnimator.OnAnimEvent(AdvancedAnimator.java:264)
at zombie.core.skinnedmodel.advancedanimation.AnimLayer.invokeAnimEvent(AnimLayer.java:211)
at zombie.core.skinnedmodel.advancedanimation.AnimLayer.updateInternal(AnimLayer.java:419)
at zombie.GameProfiler.invokeAndMeasure(GameProfiler.java:166)
at zombie.core.skinnedmodel.advancedanimation.AnimLayer.Update(AnimLayer.java:323)
at zombie.core.skinnedmodel.advancedanimation.AdvancedAnimator$SubLayerSlot.update(AdvancedAnimator.java:665)
at zombie.core.skinnedmodel.advancedanimation.AdvancedAnimator.updateInternal(AdvancedAnimator.java:403)
at zombie.GameProfiler.invokeAndMeasure(GameProfiler.java:166)
at zombie.core.skinnedmodel.advancedanimation.AdvancedAnimator.update(AdvancedAnimator.java:368)
at zombie.characters.IsoGameCharacter.postUpdateInternal(IsoGameCharacter.java:12087)
at zombie.util.lambda.Invokers$Params1$CallbackStackItem.run(Invokers.java:37)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:71)
at zombie.core.profiling.AbstractPerformanceProfileProbe.lambda$invokeAndMeasure$0(AbstractPerformanceProfileProbe.java:83)
at zombie.util.lambda.Stacks$Params3$CallbackStackItem.invoke(Stacks.java:230)
at zombie.util.lambda.Stacks$GenericStack.invokeAndRelease(Stacks.java:26)
at zombie.util.Lambda.capture(Lambda.java:130)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:81)
at zombie.characters.IsoGameCharacter.postupdate(IsoGameCharacter.java:12063)
at zombie.characters.IsoPlayer.postupdateInternal(IsoPlayer.java:3740)
at zombie.util.lambda.Invokers$Params1$CallbackStackItem.run(Invokers.java:37)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:71)
at zombie.core.profiling.AbstractPerformanceProfileProbe.lambda$invokeAndMeasure$0(AbstractPerformanceProfileProbe.java:83)
at zombie.util.lambda.Stacks$Params3$CallbackStackItem.invoke(Stacks.java:230)
at zombie.util.lambda.Stacks$GenericStack.invokeAndRelease(Stacks.java:26)
at zombie.util.Lambda.capture(Lambda.java:130)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:81)
at zombie.characters.IsoPlayer.postupdate(IsoPlayer.java:3733)
at zombie.MovingObjectUpdateSchedulerUpdateBucket.postupdate(MovingObjectUpdateSchedulerUpdateBucket.java:97)
at zombie.MovingObjectUpdateScheduler.postupdate(MovingObjectUpdateScheduler.java:168)
at zombie.CollisionManager.resolveContactsInternal(CollisionManager.java:411)
at zombie.util.lambda.Invokers$Params1$CallbackStackItem.run(Invokers.java:37)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:71)
at zombie.core.profiling.AbstractPerformanceProfileProbe.lambda$invokeAndMeasure$0(AbstractPerformanceProfileProbe.java:83)
at zombie.util.lambda.Stacks$Params3$CallbackStackItem.invoke(Stacks.java:230)
at zombie.util.lambda.Stacks$GenericStack.invokeAndRelease(Stacks.java:26)
at zombie.util.Lambda.capture(Lambda.java:130)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:81)
at zombie.CollisionManager.ResolveContacts(CollisionManager.java:236)
at zombie.iso.IsoWorld.updateInternal(IsoWorld.java:3502)
at zombie.util.lambda.Invokers$Params1$CallbackStackItem.run(Invokers.java:37)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:71)
at zombie.core.profiling.AbstractPerformanceProfileProbe.lambda$invokeAndMeasure$0(AbstractPerformanceProfileProbe.java:83)
at zombie.util.lambda.Stacks$Params3$CallbackStackItem.invoke(Stacks.java:230)
at zombie.util.lambda.Stacks$GenericStack.invokeAndRelease(Stacks.java:26)
at zombie.util.Lambda.capture(Lambda.java:130)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:81)
at zombie.iso.IsoWorld.update(IsoWorld.java:3427)
at zombie.gameStates.IngameState.updateInternal(IngameState.java:1617)
at zombie.gameStates.IngameState.update(IngameState.java:1333)
at zombie.gameStates.GameStateMachine.update(GameStateMachine.java:101)
at zombie.GameWindow.logic(GameWindow.java:298)
at zombie.core.profiling.AbstractPerformanceProfileProbe.invokeAndMeasure(AbstractPerformanceProfileProbe.java:71)
at zombie.GameWindow.frameStep(GameWindow.java:765)
at zombie.GameWindow.run_ez(GameWindow.java:667)
at zombie.GameWindow.mainThread(GameWindow.java:495)
at java.base/java.lang.Thread.run(Unknown Source)
`