Remove product load in helper

[milansimek]

The following part contains a product load, which slows everything down:

https://github.com/fheyer/sphinxsearch/blob/master/app/code/community/Gfe/SphinxSearch/Helper/Data.php#L99

It's better to replace it with:

if ($entity_id)
            {
                $categoryCollection = Mage::getResourceModel('catalog/category_collection')
                    ->clear()
                    ->joinField('product_id',
                        'catalog/category_product',
                        'product_id',
                        'category_id = entity_id',
                        null)
                    ->addFieldToFilter('product_id', (int)$entity_id)
                    ->addNameToResult()
                ;
                    foreach ($categoryCollection as $item) {
                        $categories[] = $item->getName();
                    }
            }