Thickbox should not depend on imagecache

Currently thickbox has an undocumented dependency on image cache. The theme function should be:

function thickbox_theme() {
  $theme = array(
    'imagefield_image_imagecache_thickbox' => array(
      'arguments' => array('namespace' => NULL, 'field' => NULL, 'path' => NULL, 'alt' => NULL, 'title' => NULL, 'gid' => NULL, 'attributes' => NULL),
    ),
  );

  if (module_exists('imagecache')) {
    foreach (imagecache_presets() as $preset) {
      $theme['thickbox_formatter_'. $preset['presetname'] .'_thickbox'] = array(
        'function' => 'theme_thickbox_formatter',
        'arguments' => array('element' => NULL),
      );
    }
  }

  return $theme;
}

instead of

function thickbox_theme() {
  $theme = array(
    'imagefield_image_imagecache_thickbox' => array(
      'arguments' => array('namespace' => NULL, 'field' => NULL, 'path' => NULL, 'alt' => NULL, 'title' => NULL, 'gid' => NULL, 'attributes' => NULL),
    ),
  );

  foreach (imagecache_presets() as $preset) {
    $theme['thickbox_formatter_'. $preset['presetname'] .'_thickbox'] = array(
      'function' => 'theme_thickbox_formatter',
      'arguments' => array('element' => NULL),
    );
  }

  return $theme;
}

This causes update.php not to work for users without image cache if this is not implemented. Therefore it is critical.