Custom Iron Bars help!

Hello, I am trying to make an iron bars block that can be filed away by a file item. But through using BlockPane as my super class, I get this error upon placing the block in the world or entering a world with the block already placed.

http://pastebin.com/S1XS4e8r

Heres my code:

package io.github.keegandeathman.portalcube.blocks;

import io.github.keegandeathman.portalcube.items.ItemFile;
import io.github.keegandeathman.portalcube.tileentity.TileEntityIronBarFile;
import net.minecraft.block.Block;
import net.minecraft.block.BlockPane;
import net.minecraft.block.ITileEntityProvider;
import net.minecraft.block.material.Material;
import net.minecraft.client.renderer.texture.IIconRegister;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.item.ItemStack;
import net.minecraft.tileentity.TileEntity;
import net.minecraft.world.World;

public class BlockIronBarsFile extends BlockPane implements ITileEntityProvider
{

private static String tex = "portalcube:blockIronBars";

public BlockIronBarsFile(Material p_i45394_1_) 
{
	super("portalcube:blockIronBarsBroke", "portalcube:blockIronBarsBroke", p_i45394_1_, false);
	// TODO Auto-generated constructor stub
}


@Override
public boolean onBlockActivated(World world, int x, int y, int z, EntityPlayer player, int par5, float par6, float par7, float par8)
{
	ItemStack itemStack = player.getCurrentEquippedItem();
	if(!world.isRemote)
	{
		if(itemStack.getItem() instanceof ItemFile)
		{
			TileEntityIronBarFile te = (TileEntityIronBarFile) world.getTileEntity(x, y, z);
			te.triesRemaining -=1;
			if(te.triesRemaining == 0)
			{
				world.setBlockToAir(x, y, z);
			}
			else
			{
				tex = "portalcube:blockIronBarsBroke" + te.triesRemaining;
			}

			System.out.println(te.triesRemaining);
			return true;
		}
	}
	return false;
}


@Override
public void registerBlockIcons(IIconRegister par1IconRegister)
    {
        // blockIcon - blockIcon
        this.blockIcon = par1IconRegister.registerIcon(tex);
    }


@Override
public TileEntity createNewTileEntity(World var1, int var2) {
	// TODO Auto-generated method stub
	return new TileEntityIronBarFile();
}

}