not very helpful error when executing -set commands with incorrect server tag

example command:

{'arguments': {'remote': {'type': 'mysql'},
               'server-tags': ['abc'],
               'subnets': [{'id': 1,
                            'interface': 'enp0s9',
                            'pools': [{'pool': '2001:db8:1::1-2001:db8:1::10'}],
                            'shared-network-name': '',
                            'subnet': '2001:db8:1::/64'}]},
 'command': 'remote-subnet6-set'}

result:

{
  "result": 1,
  "text": "unable to execute for <INSERT INTO dhcp6_subnet_server(  subnet_id,  modification_ts,  server_id) VALUES (?, ?, (SELECT id FROM dhcp6_server WHERE tag = ?))>, reason: Column 'server_id' cannot be null (error code 1048)"
}

and at this point server tag "abc" is missing from database. This error should say something like Server tag not existing not Column 'server_id' cannot be null

kea config:

{
    "Control-agent": {
        "control-sockets": {
            "dhcp6": {
                "socket-name": "/home/wlodek/installed/git/var/run/kea/control_socket",
                "socket-type": "unix"
            }
        },
        "http-host": "192.168.51.3",
        "http-port": 8000
    },
    "Dhcp6": {
        "config-control": {
            "config-databases": [
                {
                    "name": "keadb",
                    "password": "keapass",
                    "type": "mysql",
                    "user": "keauser"
                }
            ]
        },
        "control-socket": {
            "socket-name": "/home/wlodek/installed/git/var/run/kea/control_socket",
            "socket-type": "unix"
        },
        "hooks-libraries": [
            {
                "library": "/home/wlodek/installed/git/lib/kea/hooks/libdhcp_cb_cmds.so"
            },
            {
                "library": "/home/wlodek/installed/git/lib/kea/hooks/libdhcp_mysql_cb.so"
            }
        ],
        "interfaces-config": {
            "interfaces": [
                "enp0s9"
            ]
        },
        "lease-database": {
            "type": "memfile"
        },
        "loggers": [
            {
                "debuglevel": 99,
                "name": "kea-dhcp6",
                "output_options": [
                    {
                        "output": "/home/wlodek/installed/git/var/log/kea.log"
                    }
                ],
                "severity": "DEBUG"
            }
        ],
        "server-tag": "abc"
    }
}

wlodek@debian9-64-2:sbin $ ./kea-dhcp6 -V
1.6.0-beta-git
git 5511725555138213de4f48dc1091d65b5db47034
linked with:
log4cplus 1.1.2
OpenSSL 1.0.2s  28 May 2019
database:
MySQL backend 8.1, library 10.1.37-MariaDB
PostgreSQL backend 5.1, library 90613
Memfile backend 2.1