$elements['responsive_image_style'] = [
'#title' => t('Responsive image style'),
'#type' => 'select',
- '#default_value' => $this->getSetting('responsive_image_style'),
+ '#default_value' => $this->getSetting('responsive_image_style') ?: NULL,
'#required' => TRUE,
'#options' => $responsive_image_options,
'#description' => [