Back ordered products in cart verification do not check Manage Stock attribute

[FredericMartinez]

In app/code/community/Affirm/Affirm/Helper/Data.php you don't check if every product in quote have Manage Stock active or not.

So even if a product has Manage Stock to Yes but behind the woods has also Backorders to Allow Qty Below 0, Affirm will be disabled.

<?php
// line 149

/**
 * Skip promo message for back ordered products cart
 *
 * @param null $quote
 * @return bool
 */
public function isDisableQuoteBackOrdered($quote = null)
{
    if (null === $this->_disabledBackOrderedCart) {
        if (!Mage::helper('affirm')->isDisableForBackOrderedItems()) {
            $this->_disabledBackOrderedCart = false;
            return $this->_disabledBackOrderedCart;
        }
        if (null === $quote) {
            $quote = Mage::helper('checkout/cart')->getQuote();
        }
        foreach ($quote->getAllItems() as $quoteItem) {
            $inventory = Mage::getModel('cataloginventory/stock_item')->loadByProduct($quoteItem->getProduct());
            if ($inventory->getBackorders() && (($inventory->getQty() - $quoteItem->getQty()) < 0)) {
                $this->_disabledBackOrderedCart = true;
                break;
            }
        }
        Mage::register('affirm_disabled_backordered', $this->_disabledBackOrderedCart);
    }
    return $this->_disabledBackOrderedCart;
}