Got a problem by rightclicking the Item :/

Lex_ItemLexicon

package NLexicon.items;

import net.minecraft.client.renderer.texture.IconRegister;
import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.inventory.IInventory;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.world.World;
import NLexicon.Lex_Main;
import cpw.mods.fml.common.network.FMLNetworkHandler;
import cpw.mods.fml.relauncher.Side;
import cpw.mods.fml.relauncher.SideOnly;

public class Lex_ItemLexicon extends Item implements IInventory {

	public Lex_ItemLexicon(int id) {
		super(id);
		setCreativeTab(CreativeTabs.tabTools);
		setMaxStackSize(1);		
	}
	
	private static ItemStack[] slots = new ItemStack[1];

	@SideOnly(Side.CLIENT)
	public void registerIcons(IconRegister iconRegister)
	{
		this.itemIcon = iconRegister.registerIcon(Lex_Main.modid + ":" + this.getUnlocalizedName().substring(5));
	}
	
//	public ItemStack onItemRightClick(ItemStack itemstack, World world, EntityPlayer player)
//	{
//		if (!itemstack.equals(Lex_Main.lexicon)) return null;
//		FMLNetworkHandler.openGui(player, Lex_Main.instance, Lex_Main.guiIdLexicon, world, (int) player.posX, (int) player.posY, (int) player.posZ);
//		return itemstack;
//	}
	
	public ItemStack onItemRightClick(ItemStack item, World world, EntityPlayer player)
	{
		if (item != player.inventory.getCurrentItem()) return null;
		player.openGui(Lex_Main.instance, Lex_Main.guiIdLexicon, world, (int)player.posX, (int)player.posY, (int)player.posZ);
		return item;
	}

	public int getSizeInventory() {
		return this.slots.length;
	}

	public ItemStack getStackInSlot(int slot) {
		return slots[slot];
	}

	public ItemStack decrStackSize(int i, int j) {
		return null;
	}

	public ItemStack getStackInSlotOnClosing(int slot) {
		return this.slots[slot] = null;
	}

	public void setInventorySlotContents(int slot, ItemStack itemstack) {
		this.slots[slot] = null;
		this.slots[slot] = itemstack.copy();
	}

	public String getInvName() {
		return null;
	}

	public boolean isInvNameLocalized() {
		return false;
	}

	public int getInventoryStackLimit() {
			return 64;
	}

	public void onInventoryChanged() {
		
	}

	public boolean isUseableByPlayer(EntityPlayer entityplayer) {
		return true;
	}

	public void openChest() {	
	}

	public void closeChest() {
	}

	public boolean isItemValidForSlot(int i, ItemStack itemstack) {
		return true;
	}
}

-=(*/ ERRORS BY RIGHT CLICKING THE ITEM *\)=-

---- Minecraft Crash Report ----
// Quite honestly, I wouldn't worry myself about that.

Time: 09.11.13 17:25
Description: Ticking memory connection

java.lang.ArrayIndexOutOfBoundsException: 4
	at net.minecraft.entity.player.InventoryPlayer.getStackInSlot(InventoryPlayer.java:658)
	at net.minecraft.inventory.Slot.getStack(Slot.java:91)
	at net.minecraft.inventory.Container.getInventory(Container.java:69)
	at net.minecraft.inventory.Container.addCraftingToCrafters(Container.java:55)
	at cpw.mods.fml.common.network.NetworkRegistry.openRemoteGui(NetworkRegistry.java:321)
	at cpw.mods.fml.common.network.FMLNetworkHandler.openGui(FMLNetworkHandler.java:352)
	at net.minecraft.entity.player.EntityPlayer.openGui(EntityPlayer.java:2480)
	at NLexicon.items.Lex_ItemLexicon.onItemRightClick(Lex_ItemLexicon.java:41)
	at net.minecraft.item.ItemStack.useItemRightClick(ItemStack.java:176)
	at net.minecraft.item.ItemInWorldManager.tryUseItem(ItemInWorldManager.java:353)
	at net.minecraft.network.NetServerHandler.handlePlace(NetServerHandler.java:540)
	at net.minecraft.network.packet.Packet15Place.processPacket(Packet15Place.java:79)
	at net.minecraft.network.MemoryConnection.processReadPackets(MemoryConnection.java:89)
	at net.minecraft.network.NetServerHandler.networkTick(NetServerHandler.java:141)
	at net.minecraft.network.NetworkListenThread.networkTick(NetworkListenThread.java:54)
	at net.minecraft.server.integrated.IntegratedServerListenThread.networkTick(IntegratedServerListenThread.java:109)
	at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:689)
	at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:585)
	at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:129)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:482)
	at net.minecraft.server.ThreadMinecraftServer.run(ThreadMinecraftServer.java:16)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at net.minecraft.entity.player.InventoryPlayer.getStackInSlot(InventoryPlayer.java:658)
	at net.minecraft.inventory.Slot.getStack(Slot.java:91)
	at net.minecraft.inventory.Container.getInventory(Container.java:69)
	at net.minecraft.inventory.Container.addCraftingToCrafters(Container.java:55)
	at cpw.mods.fml.common.network.NetworkRegistry.openRemoteGui(NetworkRegistry.java:321)
	at cpw.mods.fml.common.network.FMLNetworkHandler.openGui(FMLNetworkHandler.java:352)
	at net.minecraft.entity.player.EntityPlayer.openGui(EntityPlayer.java:2480)
	at NLexicon.items.Lex_ItemLexicon.onItemRightClick(Lex_ItemLexicon.java:41)
	at net.minecraft.item.ItemStack.useItemRightClick(ItemStack.java:176)
	at net.minecraft.item.ItemInWorldManager.tryUseItem(ItemInWorldManager.java:353)
	at net.minecraft.network.NetServerHandler.handlePlace(NetServerHandler.java:540)
	at net.minecraft.network.packet.Packet15Place.processPacket(Packet15Place.java:79)
	at net.minecraft.network.MemoryConnection.processReadPackets(MemoryConnection.java:89)
	at net.minecraft.network.NetServerHandler.networkTick(NetServerHandler.java:141)

-- Ticking connection --
Details:
	Connection: net.minecraft.network.NetServerHandler@51330b8a
Stacktrace:
	at net.minecraft.network.NetworkListenThread.networkTick(NetworkListenThread.java:54)
	at net.minecraft.server.integrated.IntegratedServerListenThread.networkTick(IntegratedServerListenThread.java:109)
	at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:689)
	at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:585)
	at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:129)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:482)
	at net.minecraft.server.ThreadMinecraftServer.run(ThreadMinecraftServer.java:16)

-- System Details --
Details:
	Minecraft Version: 1.6.2
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_40, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 746220752 bytes (711 MB) / 1037959168 bytes (989 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 3 total; -Xincgc -Xmx1024M -Xms1024M
	AABB Pool Size: 3534 (197904 bytes; 0 MB) allocated, 3371 (188776 bytes; 0 MB) used
	Suspicious classes: FML and Forge are installed
	IntCache: cache: 1, tcache: 0, allocated: 2, tallocated: 62
	FML: MCP v8.04 FML v6.2.62.871 Minecraft Forge 9.10.1.871 6 mods loaded, 6 mods active
	mcp{8.04} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	FML{6.2.62.871} [Forge Mod Loader] (bin) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	Forge{9.10.1.871} [Minecraft Forge] (bin) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	lexicon{Development 0.0.1} [Minecraft Lexicon] (bin) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	nomatter{Development 0.0.1} [No Matter] (bin) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	NM_TCon_CrossoverAddon{Development 0.0.1} [IC², TCon & NM Crossover Addon] (bin) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 620 (34720 bytes; 0 MB) allocated, 584 (32704 bytes; 0 MB) used
	Player Count: 1 / 8; [EntityPlayerMP['Player384'/304, l='New World', x=-252,91, y=64,00, z=183,19]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Definitely; Client brand changed to 'fml,forge'