Spieler Potion Effect geben

@Override
    public void onUpdate(ItemStack stack, World worldIn, Entity entityIn, int itemSlot, boolean isSelected) {
        super.onUpdate(stack, worldIn, entityIn, itemSlot, isSelected);
        if (entityIn instanceof EntityPlayer) {
            EntityPlayer player = ((EntityPlayer) entityIn);
            boolean gegeben = false;
            String itemString = registry.teer_eimer.toString();
            PotionEffect unluckEffect = new PotionEffect(Potion.getPotionById(27), 300, 1);
            if (player.getHeldItemMainhand() != null) {
                if (player.getHeldItemMainhand().getItem().toString().contains(itemString)) {
                    player.addPotionEffect(unluckEffect);
                    if (gegeben == false) {
                        gegeben = true;
                    }
                }
            }
            if (player.getHeldItemOffhand() != null) {
                    if (gegeben == false){
                        if (player.getHeldItemOffhand().getItem().toString().contains(itemString)) {
                            player.addPotionEffect(unluckEffect);
                            gegeben = true;
                        }
                    }
                }
            }
        }