Problem with a drop down list of tags taking to wrong links

I am trying to make a drop down list of the tags. I found the following code, and while the list is accurate, when I select on one it the page doesnt work.

For example, it takes me to: https://aaaa.com/?cat=16
Instead of: https://aaa.com/tag/midi/

Here is the code:

<h2><?php _e('Posts by Tags'); ?></h2>
<form action="<?php bloginfo('url'); ?>/" method="get">
<div>
<?php
$select = wp_dropdown_categories('taxonomy=post_tag&show_option_none=Select tag&show_count=1&orderby=name&echo=0');
$select = preg_replace("#<select([^>]*)>#", "<select$1 onchange='return this.form.submit()'>", $select);
echo $select;
?>
<noscript><div><input type="submit" value="View" /></div></noscript>
</div></form>