Wordpress - Check if Current Category has Children

There may or may not be a better way to do this, but here's how I would do it:

$term = get_queried_object();

$children = get_terms( $term->taxonomy, array(
'parent'    => $term->term_id,
'hide_empty' => false
) );
// print_r($children); // uncomment to examine for debugging
if($children) { // get_terms will return false if tax does not exist or term wasn't found.
    // term has children
}

If current taxonomy term has children the get_terms function will return an array, otherwise it will return false.

Tested and works on my local vanilla install with Custom Post Type UI plugin used for CPT generation.

There's also a generic WP possibility to do this via get_term_children.

<?php
$children = get_term_children($termId, $taxonomyName);

if( empty( $children ) ) {
    //do something here
}