Warning: Undefined array key "data"

Problem/Motivation

When creating/editing a content, using the referenced view field it returns a warning for using an empty array.

Warning: Undefined array key "data" in Drupal\viewsreference\Plugin\Field\FieldType\ViewsReferenceItem->setValue() (line 97 of /var/www/html/web/modules/contrib/viewsreference/src/Plugin/Field/FieldType/ViewsReferenceItem.php)

Steps to reproduce

1. Install the module.
2. Structure » Content types » Basic page » Manage fields » Add views reference field
3. Configure the field (in my case, block and checked some "Preselect View Options")
4. Create a new basic page content
5. Select random view and check the log

Proposed resolution

Check if "$values['data']" is set.

    $data = unserialize($values['data'], ['allowed_classes' => FALSE]);
    if (isset($data['argument']) && $data['argument'] === '') {
      $data['argument'] = NULL;
      $values['data']   = serialize($data);
    }

ViewsReferenceItem.php (line 97)

Remaining tasks

User interface changes

API changes

Data model changes