Webplayer crashes when logged in with Firefox with a custom user agent.

[Scratchcat]

Plan

Premium

UK

Device

Generic Desktop

Operating System

Debian Linux

My Question or Issue

The webpage player crashes when logged in with a custom user agent string.

Steps to reproduce:

Using Firefox 78.0.2 and the User-Agent Switcher extension.

Set user agent to "Mozilla/5.0 (X11; Linux i586; rv:78.0.2) Gecko/20100101 Firefox/78.0.2"

Clear cookies and site data.

Login to spotify.com

Open a link to a playlist

Expected outcome:

The player shows the playlist

Actual outcome:

A black screen with an error message in the console:

Failed to load ‘https://api.spotify.com/v1/me’. A ServiceWorker passed a promise to FetchEvent.respondWith() that rejected with ‘Error: no-response :: [{"url":"https://api.spotify.com/v1/me"}]’.

Notes:
Doing the same without a custom user agent, without logging in or using chromium works fine.

Only appears to occur when a three part version is used. e.g. 78.0.2 crashes while 78.0 doesn't.