Box art url is null

API
3

The docs

Match the API output OP has provided

You should JSON parse the response, and the extract resp->data[0]->box_art_url and then substritute/string replace {width} and {height} for number for the dimension of image you need.

So

https://static-cdn.jtvnw.net/ttv-boxart/PLAYERUNKNOWN%27S%20BATTLEGROUNDS-{width}x{height}.jpg

becomes

https://static-cdn.jtvnw.net/ttv-boxart/PLAYERUNKNOWN%27S%20BATTLEGROUNDS-200x300.jpg