File can’t save or upload

I use piklist on wordpress 5.1

Try to create a slider widget with the file type, but it can’t be saved.

Is piklist not compatible with the latest wordpress?

Need help.

Slider-form.php

piklist('field', array(
    'type' => 'text',
    'field' => 'my_text',
    'label' => 'Text',
    'attributes' => array(
      'class' => 'regular-text'
    )
  ));
piklist( 'field', array(
  'type'    => 'group',
  'field'   => 'slider_group',
  'add_more'  => true,
  'label'   => __('Slider Expert4you', 'expert4you'),
  'fields'  => array(
    array(
      'type'  => 'file',
      'field' => 'slider_image',
      'label' => __('Slides', 'expert4you'),
      'columns' => 12,
    )
  )
) );

Slider.php

<?php
/*  
Title:  Slider Widget
Description:  Slider Widget
Standalone: true
*/?>
<?php echo $before_widget; ?>

<?php echo $before_title; ?>

<?php echo $settings['my_text']; ?>

<?php echo $after_title; ?>

<?php echo $settings['slider_group']; ?>

<?php echo $after_widget; ?>