search from category not working

search from category not working

?query=&advert_category=xxxx

<div class="adverts-search">
    <form action="" method="get">
        <div class="advert-input">
            <input type="text" name="query" placeholder="<?php _e("search ", "adverts") ?>" value="<?php esc_attr_e($query) ?>" />
        </div>

<div class="advert-input">
<?php
function get_terms_dropdown_price($taxonomies, $args){
	$myterms = get_terms($taxonomies, $args);
	$optionname = "advert_category";
	$emptyvalue = "";
	$output ="<select  name='".$optionname."'><option selected='".$selected."' value='".$emptyvalue."'>all Category</option>'";

	foreach($myterms as $term){
		$term_taxonomy=$term->YOURTAXONOMY; //CHANGE ME
		$term_slug=$term->slug;
		$term_name =$term->name;
		$link = $term_slug;
		$output .="<option name='".$link."' value='".$link."'>".$term_name."</option>";
	}
	$output .="</select>";
return $output;
}

$taxonomies = array('advert_category');
$args = array('order'=>'ASC','hide_empty'=>FALSE);
echo get_terms_dropdown_price($taxonomies, $args);

?>

        </div>

        <div style="text-align: right; padding: 0 0.5em 0.5em 0; ">
            <input type="submit" value="<?php _e("", "adverts") ?>" />
        </div>
    </form>
</div>

https://wordpress.org/plugins/wpadverts/