Empty string on no username

Describe the bug
When I send a request to /api/auth/register with the following json body:

{
  "username": "Hi",
  "consent": false
}

I get this error:

{
  "code": 50035,
  "message": "Invalid Form Body",
  "errors": {
    "consent": {
      "_errors": [
        {
          "message": "You must agree to the Terms of Service and Privacy Policy.",
          "code": "CONSENT_REQUIRED"
        }
      ]
    }
  }
}

So far, so good.
However, if I don't supply a username, like this:

{
  "consent": false
}

, the response looks like this:

{
  "code": 50035,
  "message": "Invalid Form Body",
  "errors": {
    "": {
      "_errors": [
        {
          "message": "must have required property 'username'",
          "code": "required"
        }
      ]
    }
  }
}

The field under "errors" is just an empty string. Is this supposed to be like that?

System Information (please complete the following information):

• OS: Arch btw
• Node Version: Node v19.9.0
• Python 3 Version: Python 3.10.10

Env and Software info

• Branch (if release is not applicable): main
• Commit Hash: 174d34c376a6a94c88b163cf46f76f2b6e52e633
• Database: SQLite
• Reverse Proxy: n.a.
• Thread Count:

Additional context
i hate json i hate json
i hate json
i hate json
i hate json
i hate json

Start at the /api/auth/register entry point and reproduce the two request bodies shown in the issue. Trace how validation errors are mapped into the response, then verify that the missing-username case reports the intended field consistently and that both consent and username validation remain covered.