如何解决WooCommerce中的PHP断言失败错误？

对于我托管的网站，我在Apache错误日志中遇到以下错误：

PHP警告：assert（）[function.assert]：在第259行的/wp content/plugins/woocmerce cart reports/models/AV8_cart_receive.PHP中断言失败

该网站正在运行WoodPress 3.6.1和WooCommerce 2.0.14。该错误与Cart Reports插件有关，我正在运行该插件的1.0.2版

这里是来自…/plugins/woocmerce cart reports/models/AV8_cart_receive.php的第259行

assert($this->post_id >0); //Make sure we're working with a valid post id.

下面是上下文的整个函数：

 public function update_receipt() {
    assert($this->sid != '');
            global $wpdb;
            global $offset;
            assert($offset != '' && is_numeric($offset));

            assert($this->post_id >0); //Make sure we're working with a valid post id.
            update_post_meta($this->post_id, 'av8_cartitems', $this->add_titles_to_cart_items($this->products));
            $post_updated = array(
               'ID' => $this->post_id,
               'post_title'=>$this->post_title,
               'post_author'=>$this->post_author,
               'post_date' => $this->post_date,
               'post_type' => 'carts'

            );

            wp_update_post($post_updated);
            update_post_meta($this->post_id, "av8_last_updated", gmmktime());
    }

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我应该如何进行故障排除和/或解决此错误？

反向工作。$this->post_id从何而来，为什么此时不大于0？