Code d'erreur

[14:24:27 ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'mute' in plugin antikikoo v1.0
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[spigot.jar:git-Spigot-c3e4052-1953f52]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[spigot.jar:git-Spigot-c3e4052-1953f52]
        at org.bukkit.craftbukkit.v1_10_R1.CraftServer.dispatchCommand(CraftServer.java:646) ~[spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.PlayerConnection.handleCommand(PlayerConnection.java:1351) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.PlayerConnection.a(PlayerConnection.java:1186) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.PacketPlayInChat.a(PacketPlayInChat.java:45) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.PacketPlayInChat.a(PacketPlayInChat.java:1) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.PlayerConnectionUtils$1.run(SourceFile:13) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_101]
        at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_101]
        at net.minecraft.server.v1_10_R1.SystemUtils.a(SourceFile:45) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:733) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.DedicatedServer.D(DedicatedServer.java:399) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:672) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:571) [spigot.jar:git-Spigot-c3e4052-1953f52]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_101]
Caused by: java.lang.NullPointerException
        at fr.zitugi.antikikoo.MuteCommand.onCommand(MuteCommand.java:21) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spigot.jar:git-Spigot-c3e4052-1953f52]
        ... 15 more