Changing Thumbnail size > WARNING

Changing Thumbnail size > WARNING

Hello there!
I was happily configuring my Jshooping Image/Video in the back-end. When I changed the "Category thumbnail height" from 0 to 300, then saved, I got the following warning:

Warning: Creating default object from empty value in C:\xampp\htdocs\shop\components\com_jshopping\tables\config.php on line 50

What is the problem? How can I solve it?

---

Aw: Changing Thumbnail size > WARNING

The Problem is SOLVED.

First of all, it happened after I changed the currency actually, not the image size (But I didn't notice it until I saved the image configuration)

Second, the solution:
If you add a new currency, and delete the USD (the default currency), then u have to change the new default currency from:
" Configuration>> other confg >> Default frontend currency ID "