[Bug]: `Failed sending heartbeat, got: undefined`

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

I saw this in my browser console. I don't know if/how it's a bug but it smells like one.

PUT https://localhost/ocs/v2.php/apps/user_status/api/v1/heartbeat?format=json returns 204.

Steps to reproduce

1. Open a Nextcloud page
2. Wait and watch the browser console

Expected behavior

No status heartbeat failure

Installation method

None

Nextcloud Server version

master

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

Failed sending heartbeat, got: undefined UserStatus.vue:210
Failed sending heartbeat, got: undefined UserStatus.vue:210
Failed sending heartbeat, got: undefined UserStatus.vue:210

Additional info

No response

Start at UserStatus.vue line 210 and inspect how the heartbeat request to /ocs/v2.php/apps/user_status/api/v1/heartbeat?format=json handles the 204 response. Reproduce by opening a Nextcloud page and waiting for the browser console message; done means a successful heartbeat no longer reports a failure for this response.