[21:53:47 ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'duel' in plugin ProPractice v6.7
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[custom.jar:git-Spigot-21fe707-e1ebe52]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[custom.jar:git-Spigot-21fe707-e1ebe52]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand(CraftServer.java:641) ~[custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.PlayerConnection.handleCommand(PlayerConnection.java:1162) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:997) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:45) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:1) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_181]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_181]
        at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:44) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:715) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [custom.jar:git-Spigot-21fe707-e1ebe52]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181]
Caused by: java.lang.NullPointerException
        at sv.file14.propractice.iIIIiIIIIIiiiIiiIIIií.<init>(Unknown Source) ~[?:?]
        at sv.file14.propractice.IiIIIIiiiiIIIIiIiiIií.<init>(Unknown Source) ~[?:?]
        at sv.file14.propractice.IIiiiIIIIIiIiiiIiIIIí.IiIIiIiIIIIIIIIIiiIií(Unknown Source) ~[?:?]
        at sv.file14.propractice.iIiIIiiIIIIIiIIiiiiIí.onCommand(Unknown Source) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[custom.jar:git-Spigot-21fe707-e1ebe52]
        ... 15 mor