/**
 * Implements hook_image_style_delete().
 */
function {{ machine_name }}_image_style_delete($style) {
  // Administrators can choose an optional replacement style when deleting.
  // Update the modules style variable accordingly.
  if (isset($style['old_name']) && $style['old_name'] == variable_get('mymodule_image_style', '')) {
    variable_set('mymodule_image_style', $style['name']);
  }
}