[SEVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'backpack' in plugin BukkitInventoryTools v3.1.9
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:42)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:168)
	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:385)
	at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:777)
	at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:737)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:725)
	at org.getspout.spout.SpoutNetServerHandler.a(SpoutNetServerHandler.java:178)
	at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:33)
	at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:100)
	at org.getspout.spout.SpoutNetServerHandler.a(SpoutNetServerHandler.java:587)
	at net.minecraft.server.NetworkListenThread.a(SourceFile:108)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:536)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:434)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)
Caused by: java.lang.IllegalArgumentException: Invalid inventory size; expected 9
	at org.bukkit.craftbukkit.inventory.CraftInventory.setContents(CraftInventory.java:46)
	at dk.gabriel333.BITBackpack.BITBackpack.onCommand(BITBackpack.java:75)
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:40)
	... 14 more