That looks like a script that is only used by Gold Cart if your WP-eCommerce version is before 3.8?
if ( ( get_option( 'show_search' ) == 1 ) && ( get_option( 'show_live_search' ) == 1 ) ) {
if ( (float)WPSC_VERSION < 3.8 ) {
$siteurl = get_option( 'siteurl' );
if ( is_ssl() ) {
$siteurl = str_replace("https://", "https://", $siteurl);
}
$deps[] = 'wpsc-iautocompleter';
wp_enqueue_script( 'wpsc-iautocompleter', "{$site_url}/wp-content/plugins/" . WPSC_DIR_NAME . '/js/iautocompleter.js', array( 'jquery' ) );
}
}
If you are using a version that old you might want to consider upgrading?
Looking at the code you could also make the error go away if you turn off live search or show search in the settings.