Fix Error if meetings are cloned

[Elblinator]

Current behaviour:
if you try to clone a meeting where a user has a gender then an error is thrown

Thrown Error:

Error: user/1: Invalid fields gender (value: male) user/2: Invalid fields gender (value: female) user/3: Invalid fields gender (value: diverse)

Payload:

[
    {
        "action": "meeting.clone",
        "data": [
            {
                "meeting_id": 1
            }
        ]
    }
]

Wanted behaviour:
You should be able to clone a meeting even if there are users with a gender inside of them