Chestshop error

[SEVERE] Could not pass event BLOCK_BREAK to ChestShop
java.lang.NullPointerException
	at org.anjocaido.groupmanager.permissions.NijikoPermissionsProxy.permission(NijikoPermissionsProxy.java:180)
	at org.anjocaido.groupmanager.permissions.NijikoPermissionsProxy.has(NijikoPermissionsProxy.java:163)
	at com.Acrobot.ChestShop.Permission.has(Permission.java:32)
	at com.Acrobot.ChestShop.Permission.has(Permission.java:28)
	at com.Acrobot.ChestShop.Listeners.blockBreak.cancellingBlockBreak(blockBreak.java:30)
	at com.Acrobot.ChestShop.Listeners.blockBreak.onBlockBreak(blockBreak.java:53)
	at org.bukkit.plugin.java.JavaPluginLoader$40.execute(JavaPluginLoader.java:539)
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:58)
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:339)
	at net.minecraft.server.ItemInWorldManager.c(ItemInWorldManager.java:201)
	at net.minecraft.server.ItemInWorldManager.a(ItemInWorldManager.java:165)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:501)
	at net.minecraft.server.Packet14BlockDig.a(SourceFile:43)
	at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:93)
	at net.minecraft.server.NetworkListenThread.a(SourceFile:108)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:527)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:425)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)