CKE5: Dropdown Image Style broken

Problem/Motivation

After enabling `Allow the user to override the default view mode` the config modal will not be loaded. Error message in console: `image-style-configuration-definition-invalid`

See Error-Link.

Corresponding Object:

{
    "dropdown": {
        "name": "drupalMedia:viewMode",
        "display": "listDropdown",
        "defaultItem": "drupalElementStyle:viewMode:base_50_percent",
        "defaultText": "View mode",
        "items": [
            "drupalElementStyle:viewMode:base_100_percent",
            "drupalElementStyle:viewMode:base_100_percent_flex",
            "drupalElementStyle:viewMode:base_100_percent_landscape",
            "drupalElementStyle:viewMode:base_33_percent",
            "drupalElementStyle:viewMode:base_33_percent_flex",
            "drupalElementStyle:viewMode:base_50_percent",
            "drupalElementStyle:viewMode:base_50_percent_flex",
            "drupalElementStyle:viewMode:base_50_percent_portrait"
        ]
    }
}

Steps to reproduce

• Create responsive image styles (with breakpoints and image styles)
• Enable Drupal-Media-Icon in CKE5
• Allow option Allow the user to override the default view mode
• In Filter Settings choose some responsive image styles