Invalid JSON ( Woocommerce API )

Hi,
I’m using the Woocommerce API for like a week now, and it’s working fine, except the fact that sometimes this error is displayed: “Invalid JSON returned for https://php2-indepth.rhcloud.com/wc-api/v2/orders?….”
I’m using PHP Client Library: https://github.com/kloon/WooCommerce-REST-API-Client-Library

Any way to make this error never appear?

https://ww.wp.xz.cn/plugins/woocommerce/