Tags Dropdown Menu not working

Hi, I’d like to have a Tags Dropdown Menu showing all my tags, just like the one for Categories.

I’ve found the code on this page but when I use it, it shows nothing, do you know why it’s not working?

<?php function drop_tags()
{
    echo "<select onChange=\"document.location.href=this.options[this.selectedIndex].value;\">";
    echo "<option>Tags</option>\n";
    foreach (get_the_tags() as $tag)
    {
        echo "<option value=\"";
        echo get_tag_link($tag->term_id);
        echo "\">".$tag->name."</option>\n";
    }
    echo "</select>";
}
 ?>

Thanks for your help! 🙂