[Possible Bug] Some preview urls for tracks are null when using App Authentication

[Perjam55]

Endpoints:

• GET https://api.spotify.com/v1/tracks/
• GET https://api.spotify.com/v1/playlists/{playlistId}/tracks

Scopes:

• App Authentication (Client Credentials Flow)
• User Authentication (Authorisation Code Flow, no additional scopes)

Steps to reproduce:

1. Get authentication token using user authentication
2. Send GET to https://api.spotify.com/v1/tracks/68TJaMSstlIuOKpRr1riov?market=GB
   Preview url returns with a value
3. Get authentication token using app authentication
4. Send GET to Send GET to https://api.spotify.com/v1/tracks/68TJaMSstlIuOKpRr1riov?market=GB
   Preview url returns as null

Expected behaviour:

Preview url has a value when using both user and app authentication

Actual behaviour:

Preview url is always null for some tracks when using app authentication but not when using user authentication