Setting default image style to 'original image' in formatter In a custom formatter that I'm writing, I have a problem with default_value for an image style.

function MYMODULE_field_formatter_info() {
  return array(
    'MYMODULE_formatter' =&gt; array(
      'label' =&gt; t('My Custom Formatter'),
      'field types' =&gt; array('image'),
      'multiple values' =&gt; FIELD_BEHAVIOR_DEFAULT,
      'settings' =&gt; array(
        'trigger_image_style' =&gt; '',
      )
    ),
  );
}


function MYMODULE_field_formatter_settings_form($field, $instance, $view_mode, $form, &amp;$form_state){
  $display = $instance['display'][$view_mode];
  $settings = $display['settings'];

  $element = array();

  $image_styles = image_style_options(FALSE);
  $element['trigger_image_style'] =  array(
    '#type' =&gt; 'select',
    '#title' =&gt; t('Trigger image style:'),
    '#description' =&gt; t('Image style to be used for trigger'),
    '#default_value' =&gt; $settings['trigger_image_style'],
    '#options' =&gt; $image_styles,
  );

  return $element;
}

function MYMODULE_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
  $elements = array();
  $html = "";
  $settings = $display['settings'];

  // ensure deaults?
  if (!isset($settings['trigger_image_style'])) $settings['trigger_image_style'] = '';
  //.....
}


Seems that Drupal will return incorrect path:

image_style_url($settings['trigger_image_style'], $item['uri']);


until I explicitly set a style of my choice. The incorrect path will have double slash, as in:

http://example.com/sites/default/files/styles//public/trigger-images/test1.jpg


I thought that empty string simply means 'use original image'... How should I tell Drupal to use original image if the style is not set or is an empty string?
It is have simple solution when you want specified image_style use something like 

  image_style_url('850x450',$file-&gt;uri);


and when you don't want use any image style and want use origin image use

 file_create_url($file-&gt;uri);