[23:30:59] [Server thread/ERROR]: Could not pass event InventoryClickEvent to dtlTraders v5.1.10
org.bukkit.event.EventException: null
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:320) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:529) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:514) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.PlayerConnection.a(PlayerConnection.java:2147) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.PacketPlayInWindowClick.a(SourceFile:32) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.PacketPlayInWindowClick.a(SourceFile:10) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.PlayerConnectionUtils.lambda$0(PlayerConnectionUtils.java:19) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.TickTask.run(SourceFile:18) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeTask(SourceFile:144) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.IAsyncTaskHandlerReentrant.executeTask(SourceFile:23) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeNext(SourceFile:118) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.MinecraftServer.aZ(MinecraftServer.java:917) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.MinecraftServer.executeNext(MinecraftServer.java:910) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeAll(SourceFile:103) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.MinecraftServer.sleepForTick(MinecraftServer.java:893) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:827) [spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]
    at java.lang.Thread.run(Thread.java:748) [?:1.8.0_232]
Caused by: java.lang.NoClassDefFoundError: Could not initialize class net.wesjd.anvilgui.AnvilGUI
    at nl.thewgbbroz.dtltraders.custominventory.GUITextInputService.openTextGUI(GUITextInputService.java:90) ~[?:?]
    at nl.thewgbbroz.dtltraders.adminguis.TraitEditService$3.onClick(TraitEditService.java:354) ~[?:?]
    at nl.thewgbbroz.dtltraders.custominventory.DumbCustomInventoryService.onInventoryClickEvent(DumbCustomInventoryService.java:66) ~[?:?]
    at sun.reflect.GeneratedMethodAccessor64.invoke(Unknown Source) ~[?:?]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_232]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_232]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:316) ~[spigot-1.15.jar:git-Spigot-f39a89e-4633e6c]