Magento结账第二次额外的成功消息

When customer add product to cart and this product is removed from store, there are two messages enter image description here

How can i remove the second message about deleting product when the first message is called.

There are next functions that call the messages:

protected function _getProduct($productInfo)
{
    $product = null;
    if ($productInfo instanceof Mage_Catalog_Model_Product) {
        $product = $productInfo;
    } elseif (is_int($productInfo) || is_string($productInfo)) {
        $product = Mage::getModel('catalog/product')
            ->setStoreId(Mage::app()->getStore()->getId())
            ->load($productInfo);
    }
    $currentWebsiteId = Mage::app()->getStore()->getWebsiteId();
    if (!$product
        || !$product->getId()
        || !is_array($product->getWebsiteIds())
        || !in_array($currentWebsiteId, $product->getWebsiteIds())
    ) {
        Mage::getSingleton('checkout/session')->addSuccess(Mage::helper('checkout')->__('The product could not be found.'));
    }
    return $product;
}

and second extra message

public function addItemRemoveNotification(Varien_Event_Observer $observer)
{
    /* @var $quoteItem Advox_Sales_Model_Quote_Item */
    $quoteItem = $observer->getQuoteItem();

    if (true === boolval($quoteItem->getData('is_a_free_sample'))) {
        return $this;
    }

    Mage::getSingleton('core/session')->addSuccess(
        Mage::helper('checkout')->__("%s successfully removed from basket.", $quoteItem->getData('name'))
    );

    return $this;
}

Edit addItemRemoveNotification method:

public function addItemRemoveNotification(Varien_Event_Observer $observer)
    {
        /* @var $quoteItem Advox_Sales_Model_Quote_Item */
        $quoteItem = $observer->getQuoteItem();

        if (true === boolval($quoteItem->getData('is_a_free_sample'))) {
            return $this;
        }

        $smessages = Mage::getSingleton('checkout/session')->getMessages()->getItems();
        $firstMessageExist = false;
        foreach ($smessages as $smessage) {
             $text = $message->getText();
             if($text == 'The product could not be found.'){
                $firstMessageExist = true; 
             }
        }
        if($firstMessageExist === false){
            Mage::getSingleton('core/session')->addSuccess(
            Mage::helper('checkout')->__("%s successfully removed from basket.",     $quoteItem->getData('name'))
        );
        }

        return $this;
    }