At this moment you change it to the default Google Maps pin. Paste this code on the bottom of your theme functions.php file:

add_action('wp_footer', function() {
    ?>
    <script type="text/javascript">
        ;
        (function ($) {
            $(function () {
                if (typeof $.stecExtend !== 'function') {
                    return;
                }
                $('.stec').on('stecMapMarkerIcon', function (a, data) {
                    data.temp.stecMapMarkerIcon = '';
                });
            });
        })(jQuery);
    </script>
    <?php
});