Yea, just remove this part:
foreach ( \IPS\Db::i()->select( '*', 'cms_database_fields', array( 'field_type=?', 'CountryFieldCvh' ) ) AS $countryField )
{
$field = \IPS\cms\Fields::load( $countryField[ 'field_id' ], $countryField[ 'field_database_id' ] );
$field->delete();
}
then it should work 🙂