help

[20:09:24] [Server thread/INFO]: An unknown error occurred while attempting to perform this command
[20:09:24] [Server thread/ERROR]: Couldn't process command: 'help'
java.lang.NullPointerException
        at evilcraft.api.Helpers.isOp(Helpers.java:412) ~[Helpers.class:?]
        at evilcraft.commands.CommandEvilCraft.func_71519_b(CommandEvilCraft.java:99) ~[CommandEvilCraft.class:?]
        at net.minecraft.command.CommandHandler.func_71557_a(CommandHandler.java:219) ~[z.class:?]
        at net.minecraft.command.CommandHelp.func_71534_d(SourceFile:83) ~[au.class:?]
        at net.minecraft.command.CommandHelp.func_71515_b(SourceFile:38) ~[au.class:?]
        at net.minecraft.command.CommandHandler.func_71556_a(CommandHandler.java:94) [z.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_71333_ah(DedicatedServer.java:371) [lt.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:336) [lt.class:?]
        at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685) [li.class:?]