[03:28:58] [Server thread/INFO]: Genome issued server command: /townygui:tgui
[03:28:58] [Server thread/ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'townygui:tgui' in plugin TownyGUI v4.9.1
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:47) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:149) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at org.bukkit.craftbukkit.v1_16_R2.CraftServer.dispatchCommand(CraftServer.java:756) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.PlayerConnection.handleCommand(PlayerConnection.java:1692) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.PlayerConnection.a(PlayerConnection.java:1535) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.PacketPlayInChat.a(PacketPlayInChat.java:47) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.PacketPlayInChat.a(PacketPlayInChat.java:1) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.PlayerConnectionUtils.lambda$0(PlayerConnectionUtils.java:19) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.TickTask.run(SourceFile:18) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.IAsyncTaskHandler.executeTask(SourceFile:144) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.IAsyncTaskHandlerReentrant.executeTask(SourceFile:23) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.IAsyncTaskHandler.executeNext(SourceFile:118) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.MinecraftServer.ba(MinecraftServer.java:941) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.MinecraftServer.executeNext(MinecraftServer.java:934) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.IAsyncTaskHandler.executeAll(SourceFile:103) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.MinecraftServer.sleepForTick(MinecraftServer.java:917) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.MinecraftServer.w(MinecraftServer.java:850) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at net.minecraft.server.v1_16_R2.MinecraftServer.lambda$0(MinecraftServer.java:164) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: java.lang.IllegalArgumentException: Material cannot be null
    at org.apache.commons.lang.Validate.notNull(Validate.java:192) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:82) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:70) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:58) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:44) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    at com.mystycfalls.townygui.itemstack.ItemStackMainMenuInv.plot(ItemStackMainMenuInv.java:47) ~[TownyGUI.jar:?]
    at com.mystycfalls.townygui.commands.CommandTGUI.onCommand(CommandTGUI.java:69) ~[TownyGUI.jar:?]
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45) ~[spigot-1.16.2.jar:git-Spigot-b5a13e6-00bff02]
    ... 18 more