Error "No values to submit" when submit opening dialog without elements

[traarttra]

Summary

When I send an opendialog request without elements, e.g.:

{
  "trigger_id": "trigger_id",
  "url": "http://localhost",
  "dialog": {
    "title": "Title",
    "submit_label": "Submit",
    "notify_on_cancel": false,
    "introduction_text": "Introduction Text"
  }
}

and then submit it, I get the error "No values to submit" in the dialog.
But if I send the same request with elements, it works fine, e.g.:

{
  "trigger_id": "trigger_id",
  "url": "http://localhost",
  "dialog": {
    "title": "Title",
    "elements": [
      {
        "name": "name",
        "type": "bool",
        "optional": true
      }
    ],
    "submit_label": "Submit",
    "notify_on_cancel": false,
    "introduction_text": "Introduction Text"
  }
}

Unfortunately, I don't have server logs available.

Environment

iOS Mattermost App: 2.43.1 (Build 806)
Android Mattermost App: 2.43.1 (Build 6000806)
Server Version: 10.11.9 (Build 20127898790)