Unhandled exception executing command '1v1' in plugin Duels v1.6

Server version

Purpur 1.21.1

Duels version

1.6

Plugin list

Not there is problem

Describe the bug

Can't play game, error.

Expected behavior

[08:49:01] [Server thread/ERROR]: Command exception: /1v1 NickName org.bukkit.command.CommandException: Unhandled exception executing command '1v1' in plugin Duels v1.6 at org.bukkit.command.PluginCommand.execute(PluginCommand.java:47) ~[paper-mojangapi-1.21.1-R0.1-SNAPSHOT.jar:?] at io.papermc.paper.command.brigadier.bukkit.BukkitCommandNode$BukkitBrigCommand.run(BukkitCommandNode.java:91) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at com.mojang.brigadier.context.ContextChain.runExecutable(ContextChain.java:73) ~[brigadier-1.3.10.jar:?] at net.minecraft.commands.execution.tasks.ExecuteCommand.execute(ExecuteCommand.java:30) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.commands.execution.tasks.ExecuteCommand.execute(ExecuteCommand.java:13) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.commands.execution.UnboundEntryAction.lambda$bind$0(UnboundEntryAction.java:8) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.commands.execution.CommandQueueEntry.execute(CommandQueueEntry.java:5) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.commands.execution.ExecutionContext.runCommandQueue(ExecutionContext.java:103) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.commands.Commands.executeCommandInContext(Commands.java:451) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.commands.Commands.performCommand(Commands.java:358) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.commands.Commands.performCommand(Commands.java:345) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.commands.Commands.performCommand(Commands.java:340) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.network.ServerGamePacketListenerImpl.performUnsignedChatCommand(ServerGamePacketListenerImpl.java:2297) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.network.ServerGamePacketListenerImpl.lambda$handleChatCommand$15(ServerGamePacketListenerImpl.java:2271) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.TickTask.run(TickTask.java:18) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.util.thread.BlockableEventLoop.doRunTask(BlockableEventLoop.java:151) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.util.thread.ReentrantBlockableEventLoop.doRunTask(ReentrantBlockableEventLoop.java:24) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.MinecraftServer.doRunTask(MinecraftServer.java:1572) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.MinecraftServer.doRunTask(MinecraftServer.java:201) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.util.thread.BlockableEventLoop.pollTask(BlockableEventLoop.java:125) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.MinecraftServer.pollTaskInternal(MinecraftServer.java:1549) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.MinecraftServer.pollTask(MinecraftServer.java:1542) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.util.thread.BlockableEventLoop.managedBlock(BlockableEventLoop.java:135) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.MinecraftServer.managedBlock(MinecraftServer.java:1501) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.MinecraftServer.waitUntilNextTick(MinecraftServer.java:1508) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1353) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:333) ~[purpur-1.21.1.jar:1.21.1-2311-0fa9a50] at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?] Caused by: java.lang.NullPointerException: Cannot invoke "String.toUpperCase()" because the return value of "com.meteordevelopments.duels.config.Lang.getMessage(String)" is null at Duels-Optimised-1.6.jar/com.meteordevelopments.duels.gui.settings.buttons.OwnInventoryButton.(OwnInventoryButton.java:14) ~[Duels-Optimised-1.6.jar:?] at Duels-Optimised-1.6.jar/com.meteordevelopments.duels.gui.settings.SettingsGui.(SettingsGui.java:40) ~[Duels-Optimised-1.6.jar:?] at Duels-Optimised-1.6.jar/com.meteordevelopments.duels.setting.Settings.(Settings.java:41) ~[Duels-Optimised-1.6.jar:?] at Duels-Optimised-1.6.jar/com.meteordevelopments.duels.setting.SettingsManager.lambda$getSafely$0(SettingsManager.java:36) ~[Duels-Optimised-1.6.jar:?] at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1228) ~[?:?] at Duels-Optimised-1.6.jar/com.meteordevelopments.duels.setting.SettingsManager.getSafely(SettingsManager.java:36) ~[Duels-Optimised-1.6.jar:?] at Duels-Optimised-1.6.jar/com.meteordevelopments.duels.command.commands.duel.DuelCommand.executeFirst(DuelCommand.java:148) ~[Duels-Optimised-1.6.jar:?] at Duels-Optimised-1.6.jar/com.meteordevelopments.duels.util.command.AbstractCommand.lambda$register$0(AbstractCommand.java:113) ~[Duels-Optimised-1.6.jar:?] at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45) ~[paper-mojangapi-1.21.1-R0.1-SNAPSHOT.jar:?] ... 27 more

Steps to reproduce

/1v1 Nickname

Additional info

No response

Checklist

[X] I am running latest version of the plugin
[X] I have read the wiki to make sure it's not an issue with configuration
[ ] I ticked all of the boxes without actually reading them
[X] I have read the Compatibility wiki page and am not trying to run the plugin on an unsupported server version / platform
[X] I am willing to cooperate to get this issue resolved faster, including providing any additional information requested or testing new builds

dumbo-the-developer / Duels