Magento - Helper在模块上抛出异常

Question

We have had a working extension on our site that allows customers to request samples - the code on our category pages is :

<?php if (Mage::helper('floorsamples')->isSamplesEnabled($_product->getId())): ?>
        <a href="<?php echo $this->getUrl('samples/cart/add') . '?product=' . $_product->getId(); ?>" class="link-compare" onclick="sampleconfirm()"><img src="<?php echo $this->getSkinUrl('images/cat-freesample.png')?>" /></a>
                <?php else: ?>
                    <a href="<?php echo $_product->getProductUrl() ?>"><img src="<?php echo $this->getSkinUrl('images/cat-moreinfo.png')?>" /></a>
                <?php endif; ?>  

However, checking whether the samples option is available causes an exception to throw. The rest of the module appears to be fully functional - apart from this exception.

The functions are :

public function isSamplesEnabled($productId) {
    if (!$this->getConfigClass()->enabled) {
        return false;
    }
    $product = $this->_getProduct($productId);
    foreach ($product->getCategoryCollection() as $category) {
        if ($this->_isSamplesEnabledHelper($product, $category)) {
            return true;
        }
    }
    return false;
}

private function _isSamplesEnabledHelper($product, $category, $recursive = false) {
    $category = Mage::getModel("catalog/category")->load($category->getEntityId());
    if ($this->_getData($category)) {
        return true;
    }
    if ($recursive) {
        foreach ($category->getChildrenCategories() as $child) {
            if ($this->_isSamplesEnabledHelper($product, $child, $recursive)) {
                return true;
            }
        }
    }
    return false;
}

Thanks!

PS. Below is from the logs

a:5:{i:0;s:202:"SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1";i:1;s:6240:"#0