`display_name` is not properly set

[HeRaNO]

Description of the problem

Same issue as #2666, but #2667 cannot address this issue. Test for #2667 is poor.

Your environment

• DOMjudge 8.3.1, high probability in main branch

Steps to reproduce

1. Create a scratch DOMjudge 8.3.1 via docker.
2. Change to data_source = 1
3. Import a team with name Test Team Name

Expected behaviour

Team name should be displayed.

Actual behaviour

Seen on web, name cannot be displayed.

Seen in database, display_name is an empty string, not NULL:

Any other information that you want to share?

Scripts to create a scratch DOMjudge 8.3.1:

sudo docker run -d -it --name dj-mariadb -e MYSQL_ROOT_PASSWORD=dbrootpwd -e MYSQL_USER=domjudge -e MYSQL_PASSWORD=dbpwd -e MYSQL_DATABASE=domjudge -p 13306:3306 mariadb --max-connections=1000 --max-allowed-packet=104857600 --innodb-log-file-size=104857600
sudo docker run -d --link dj-mariadb:mariadb -it -e MYSQL_HOST=mariadb -e MYSQL_USER=domjudge -e MYSQL_DATABASE=domjudge -e MYSQL_PASSWORD=dbpwd -e MYSQL_ROOT_PASSWORD=dbrootpwd -e CONTAINER_TIMEZONE=Asia/Shanghai -p 12345:80 --name domserver domjudge/domserver

teams.json:

[
    {
        "id": "team001",
        "group_ids": [
            "participants"
        ],
        "name": "Test Team Name",
        "organization_id": "utrecht"
    }
]

[HeRaNO]

Sorry, my fault. #2667 has not backported to 8.3.1