my minecraft give me this error

>manuadd NOJ8 owner
[13:14:06 WARN]: Unexpected exception while parsing console command "manuadd NOJ8 owner"
org.bukkit.command.CommandException: Unhandled exception executing command 'manuadd' in plugin GroupManager v2.1.31 (Phoenix)
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:141) ~[craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        at org.bukkit.craftbukkit.v1_9_R1.CraftServer.dispatchCommand(CraftServer.java:645) ~[craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        at org.bukkit.craftbukkit.v1_9_R1.CraftServer.dispatchServerCommand(CraftServer.java:631) [craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        at net.minecraft.server.v1_9_R1.DedicatedServer.aL(DedicatedServer.java:438) [craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        at net.minecraft.server.v1_9_R1.DedicatedServer.D(DedicatedServer.java:401) [craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        at net.minecraft.server.v1_9_R1.MinecraftServer.C(MinecraftServer.java:660) [craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        at net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:559) [craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_66]
Caused by: java.lang.NullPointerException
        at org.anjocaido.groupmanager.GroupManager.onCommand(GroupManager.java:429) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[craftbukkit.jar:git-Spigot-90839e6-c5d27c5]
        ... 8 more
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