Addon Tuske NOT WORKING

[XX_Oscar_XX]

I have an addon called Tuske if i try to make a GUI i get this:

[ERROR] #!#!
[ERROR] #!#! [Skript] Severe Error:
[ERROR] #!#!
[ERROR] #!#! Something went horribly wrong with Skript.
[ERROR] #!#! This issue is NOT your fault! You probably can't fix it yourself, either.
[ERROR] #!#! It looks like you are using some plugin(s) that alter how Skript works (addons).
[ERROR] #!#! Here is full list of them:
[ERROR] #!#! skRayFall (https://sk.rayfall.net/) TuSKe (github.com/Tuke-Nuke/TuSKe)
[ERROR] #!#! We could not identify which of those are specially related, so this might also be Skript issue.
[ERROR] #!#! You should try disabling those plugins one by one, trying to find which one causes it.
[ERROR] #!#! If the error doesn't disappear even after disabling all listed plugins, it is probably Skript issue.
[ERROR] #!#! In that case, you will be given instruction on how should you report it.
[ERROR] #!#! On the other hand, if the error disappears when disabling some plugin, report it to author of that plugin:
[ERROR] #!#! Only if the author tells you to do so, report it to Skript's issue tracker.
[ERROR] #!#!
[ERROR] #!#! Stack trace:
[ERROR] #!#! java.lang.ClassCastException: java.util.HashMap incompatible with java.util.WeakHashMap
[ERROR] #!#! at com.github.tukenuke.tuske.util.VariableUtil.<init>(VariableUtil.java:24)
[ERROR] #!#! at com.github.tukenuke.tuske.util.VariableUtil.getInstance(VariableUtil.java:17)
[ERROR] #!#! at com.github.tukenuke.tuske.sections.gui.EffMakeGUI.execute(EffMakeGUI.java:77)
[ERROR] #!#! at com.github.tukenuke.tuske.util.EffectSection.check(EffectSection.java:54)
[ERROR] #!#! at ch.njol.skript.lang.Condition.run(Condition.java:56)
[ERROR] #!#! at ch.njol.skript.lang.Conditional.walk(Conditional.java:51)
[ERROR] #!#! at ch.njol.skript.lang.TriggerItem.walk(TriggerItem.java:89)
[ERROR] #!#! at ch.njol.skript.effects.Delay$1.run(Delay.java:109)
[ERROR] #!#! at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftTask.run(CraftTask.java:76)
[ERROR] #!#! at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:361)
[ERROR] #!#! at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:739)
[ERROR] #!#! at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406)
[ERROR] #!#! at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679)
[ERROR] #!#! at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577)
[ERROR] #!#! at java.lang.Thread.run(Thread.java:813)
[ERROR] #!#!
[ERROR] #!#! Version Information:
[ERROR] #!#! Skript: 2.4-beta9 (latest)
[ERROR] #!#! Flavor: skriptlang-github
[ERROR] #!#! Date: 2019-10-15
[ERROR] #!#! Bukkit: 1.12.2-R0.1-SNAPSHOT
[ERROR] #!#! Minecraft: 1.12.2
[ERROR] #!#! Java: 1.8.0_212 (Eclipse OpenJ9 VM openj9-0.14.0)
[ERROR] #!#! OS: Linux amd64 4.15.0-55-generic
[ERROR] #!#!
[ERROR] #!#! Server platform: Spigot
[ERROR] #!#!
[ERROR] #!#! Current node: null
[ERROR] #!#! Current item: make a gui slot [[long:2]] of gui with ([[itemtype:diamond sword]] named "PVP" >> ch.njol.skript.classes.data.DefaultConverters$13@13110c8b: itemtype -> itemstack)
[ERROR] #!#! Current trigger: right click on a sign (rightclick on [[itemtype:wall sign, floor sign or sign item]]) (PVPBot.sk, line 211)
[ERROR] #!#!
[ERROR] #!#! Thread: Server thread
[ERROR] #!#!
[ERROR] #!#! Language: english
[ERROR] #!#! Link parse mode: DISABLED
[ERROR] #!#!
[ERROR] #!#! End of Error.
[ERROR] #!#!


This is the code causing the error:
message "GUI" to the player
create a gui with id "LobbySelector" with virtual chest with 4 rows named "&4Lobby Selector":
make gui slot 2 with diamond sword named "PVP":
execute player command "/server pvp" #'on skript load' event doesn't have a 'player', but it will recognize it as it does have.
make gui slot 4 with grass named "SkyBlock":
execute player command "/server skyblock"
open gui "LobbySelector" to player