Undefined array key 0 error after update to 4.1.4 (ajax requests)

Need Help
#1

After upgrade to 4.1.4, where is mentoined some kind of new ajax, i found out, that some relations_config that uses manage, fails to open “edit/update” popup with error Undefined array key 0.

i had relation as hasMany… with relation behaviour on controller, and when i tried to open edit mode from rendered relation, it ends up with error after ajax call.

{
    "ok": false,
    "severity": "error",
    "message": "Undefined array key 0",
    "invalid": [],
    "ops": [
        {
            "op": "loadAssets",
            "type": "js",
            "assets": [
                "/modules/backend/behaviors/relationcontroller/assets/js/october.relation.js?v49fd8315",
                "/modules/backend/widgets/form/assets/js/october.form.js?v49fd8315",
                "/modules/backend/formwidgets/fileupload/assets/js/fileupload.js?v49fd8315",
                "/modules/backend/formwidgets/recordfinder/assets/js/recordfinder.js?v49fd8315",
                "/modules/backend/widgets/lists/assets/js/october.list.js?v49fd8315"
            ]
        },
        {
            "op": "loadAssets",
            "type": "css",
            "assets": [
                "/modules/backend/behaviors/relationcontroller/assets/css/relation.css?v49fd8315",
                "/modules/backend/formwidgets/fileupload/assets/css/fileupload.css?v49fd8315",
                "/modules/backend/formwidgets/recordfinder/assets/css/recordfinder.css?v49fd8315"
            ]
        }
    ],
    "redirect": null
}

EDIT:

Find out that problem probably is on file attachments.
I had used thumbOptions and offsets x: and y: and it points to probably wrong data

    public function getThumbFilename($width, $height, $options)
    {
        $options = $this->getDefaultThumbOptions($options);
        return 'thumb_' . $this->id . '_' . $width . '_' . $height . '_' . $options['offset'][0] . '_' . $options['offset'][1] . '_' . $options['mode'] . '.' . $options['extension'];
    }
#2

Can you share how you’re defining the thumbOptions in your relation config? Specifically, how are you passing the offset values?

The error “Undefined array key 0” suggests the offset might be defined as an associative array like:

'offset' => ['x' => 10, 'y' => 20]

When it should be a numeric array:

'offset' => [10, 20]

If you can share the relevant part of your config, we can confirm the issue and determine if a fix is needed in the core.