Prepopulate fails in Drupal 10

Here is the patch

I am able to replicate this issue using the attached webform and URL /form/issue-3391904?select[]=Monday&select[]=Tuesday

This regression also gives us an opportunity to refactor the code a little bit.

If the tests pass and someone does a quick manual review/test, this should be RTBC.

This is a release blocker; hence, it is critical.

jrockowitz → credited danekin → .

We should try to commit this 6.1.x to keep the codebases insync.

Automatically closed - issue fixed for 2 weeks with no activity.