Hide "Add Form" icon for custom post type (REVISED)

<?php
// http://www.gravityhelp.com/forums/topic/remove-add-form-button-from-custom-post-type-edit-page
add_action('admin_head', 'hide_add_form_icon');
function hide_add_form_icon() {
    global $post_type;
    // edited July 3 2014 to fix PHP warnings
    if ((isset($_GET['post_type']) && $_GET['post_type'] == 'directory') || ($post_type == 'directory')) {
        echo "<style type='text/css'>a#add_gform {display:none;}</style>\n";
    }
}