__list_add_tracks__() produces error #13
Description
Hi, I successfully used your tool about a year ago, but now I get an error (see screenshot). I wasn't able to debug it myself. The playlist I randomized last year had 137 songs and this year's has 140 songs (if this has anything to do with it). Authentication with the Spotify api server is successful. The first function execution at line 145 does work, but after that I only get an object that contains the 'next' field.
I can only assume Spotify changed something on their api? Maybe you can help.
