[4.1.5] (and [4.2.0_beta4]) - Webservices User API PATCH requires user group array

[aftertaf]

Steps to reproduce the issue

send a PATCH API call to the {{base_url}}/{{base_path}}/users/{{user_id}} API
Contents:
{"email":"testing@somemail.com", "some_custom_field": "0"}

Expected result

for the user specified by the {user_id}, the mail and custom field get updated to the values sent in the API call

Actual result

HTTP 500 Internal Server Error : "Save failed with the following error: You can't save a user account without selecting at least one user group."

System information (as much as possible)

PHP 8.0.18
Joomla 4.1.5 + 4.2.0-beta4-dev

Additional comments

When doing an API PATCH call to the USERS API (my use-case would be to update a custom field for the user), I cannot do the API call without specifying the "groups":["1","2","3" (etc)] array.
I don't want to updade the user groups nor to have to first GET all the USER groups in order to post them back unchanged...

[alikon]

didn't checked yet...
did it happen even without custom fields ?

[alikon]

please test #38283

[aftertaf]

Hi,
I've tried to test but I get a HTTP 500 error, whatever API call I try.
"View not found [name, type, prefix]: tags, html, api"
I think I might have broken something while trying to troubleshoot, but I am at a loss as to what...
Distracted, doing this while looking after kids, didn't note every little thing down.... Classic #fail....
Any idea which file I can check against the source branch and see what stupid thing I did ?
Sorry for being overly lame !