[08:59:02] [Server thread/ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'warn' in plugin BanManager v5.6.1
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand(CraftServer.java:641) ~[spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.PlayerConnection.handleCommand(PlayerConnection.java:1162) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.PlayerConnection.a(PlayerConnection.java:997) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:45) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(PacketPlayInChat.java:1) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.PlayerConnectionUtils$1.run(SourceFile:13) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_51]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_51]
        at net.minecraft.server.v1_8_R3.SystemUtils.a(SourceFile:44) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:714) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:653) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:556) [spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        at java.lang.Thread.run(Thread.java:745) [?:1.8.0_51]
Caused by: java.lang.IllegalArgumentException: Invalid UUID string: ichelebevonhartiv
        at java.util.UUID.fromString(UUID.java:194) ~[?:1.8.0_51]
        at me.confuser.banmanager.commands.WarnCommand.onCommand(WarnCommand.java:58) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spigot-1.8.8.jar:git-Spigot-d97e08b-880a532]
        ... 15 more