Error

Error occured while enabling Groupmanager v1.0 (2.8.2) (Phoenix).
oenix)  (Is it up to date?): There was no Default Group declared in file: Plugins
\GroupManager\worlds\ngcraft\groups.yml
java.lang.IllegalArgumentException: There was no Default Group Declared in file:
plugins\GroupManager\worlds\ngcraft\groups.yml
       at org.anjocaido.groupmanager.dataholder.WorldDataHolder.loadGroups[Worl}
dDataHolder.java:520)
       at org.anjocaido.groupmanager.dataholder.WorldDataHolder.loadGroups[Worl}
dDataHolder.java:367)
       at org.anjocaido.groupmanager.dataholder.worlds.WorldsHolder.loadWorld(W
orldsHolder.java:509
       at org.anjocaido.groupmanager.dataholder.WorldDataHolder.loadGroups[Worl}
dDataHolder.java
       at org.anjocaido.groupmanager.dataholder.worlds.WorldsHolder.initialWorl
dLoading(WorldsHolder.java:78)
       at org.anjocaido.groupmanager.dataholder.worlds.WorldsHolder.initialLoad
(WorldsHolder.java:69)
       at org.anjocaido.groupmanager.dataholder.worlds.WorldsHolder.(init)(Worl
dsHolder.java:61)
       at org.anjocaido.groupmanager.GroupManager.onEnable(GroupManager.java:12
8)
       at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java230)
       at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader
.java:1057)
       at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:199)
       at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:182

       at net.minecraft.server-MinecraftServer.t(MinecraftServer.java:357)
       at net.minecraft.server-MinecraftServer.a(minecraftServer.java:344)
       at net.minecraft.server-MinecraftServer.init(MinecraftServer.java:175
       at net.minecraft.server-MinecraftServer.run(MinecraftServer.java:408)
       at net.minecraft.serverThreadServerApplication.run(SourceFile:465