显示可配置产品库存 - Magento 1.9

Question

I'm following this answer to show the stock of my configurable products, but I'm getting an error:

error-magento

The only problem only occurs with the first item, where it shows "null".

Does anybody know how can I fix it?

Configurable.php

$simpleproduct = Mage::getModel('catalog/product')->load($productsIndex); 
$qty = (int)Mage::getModel('cataloginventory/stock_item')->loadByProduct($simpleproduct)->getQty();

$info['options'][] = array(
                    'id'        => $value['value_index'],
                    'label'     => $value['label'],
                    'price'     => $configurablePrice,
                    'oldPrice'  => $this->_prepareOldPrice($value['pricing_value'], $value['is_percent']),
                    'products'  => $productsIndex,
        'qty'       => $qty, // we are sending stock parameter so we can use it latter in drop down field

                );