WP Term Meta data: Category pictures

<?php
    /**
     * Plugin Name: Images for Categories
     * Author: Websupporter
     **/

    add_action( 'category_add_form_fields', 'fifc_add_taxonomy_picture', 10, 2 );
    add_action( 'category_edit_form_fields', 'fifc_add_taxonomy_picture', 10, 2 );
    function fifc_add_taxonomy_picture(){
        $args = func_get_args();
        if( is_string( $args[0] ) ){
            $taxonomy = $args[0];
        } else {
            $taxonomy = $args[1];
            $term = $args[0];
        }

        if( ! isset( $term ) ):
        ?>
        <div class="form-field">
            <label for="thumbnail">Kategorie-Bild</label>
            <div id="thumbnail">

                <button class="button" id="thumbnail_mediathek">&Ouml;ffnen</button>
            </div>
        </div>
        <?php
        else:
        ?>
        <tr class="form-field">
            <th scope="row"><label for="thumbnail">Kategorie-Bild</label></th>
            <td>
                <div id="thumbnail">
                <?php
                    $thumbnail = get_term_meta( $term->term_id, '_thumbnail_id', true );
                    if( $thumbnail )
                        echo wp_get_attachment_image( $thumbnail );
                ?>
                    <button class="button" id="thumbnail_mediathek">&Ouml;ffnen</button>
                </div>
                <p class="description">
                    Hier kann ein Kategoriebild hinzugef&uuml;gt werden.
                </p>
            </td>
        </tr>
        <?php
        endif;
    }

    add_action( 'edited_terms', 'fifc_edited_terms' );
    add_action( 'created_term', 'fifc_edited_terms' );
    function fifc_edited_terms( $term_id ){
        if( isset( $_POST['_thumbnail_id'] ) )
            update_term_meta( $term_id, '_thumbnail_id', (int) $_POST['_thumbnail_id'] );

    }
    add_action( 'admin_enqueue_scripts', 'fifc_tax_term_script' );
    function fifc_tax_term_script( $hook ){
        if( !in_array( $hook, array( 'edit-tags.php' ) ) )
            return;

        wp_enqueue_media();
        wp_enqueue_script( 'fifc-admin-script', plugins_url( '/script.js', __FILE__ ), array( 'jquery' ) );
    }



    function fifc_has_taxonomy_thumbnail( $term_id = null ){
        if( null == $term_id ){
            $queried_object = get_queried_object();
            if( ! isset( $queried_object->term_id ) )
                return false;

            $term_id =  $queried_object->term_id;
        }

        $thumbnail = get_term_meta( $term_id, '_thumbnail_id', true );
        return ( ! empty( $thumbnail ) );
    }

    function fifc_get_the_taxonomy_thumbnail( $term_id = null, $size = 'thumbnail', $icon = false, $attr = array() ){
        if( null == $term_id ){
            $queried_object = get_queried_object();
            if( ! isset( $queried_object->term_id ) )
                return false;

            $term_id =  $queried_object->term_id;
        }

        $thumbnail = get_term_meta( $term_id, '_thumbnail_id', true );
        if( empty( $thumbnail ) )
            return false;

        return wp_get_attachment_image( $thumbnail, $size, $icon, $attr );
    }
        function fifc_the_taxonomy_thumbnail( $term_id = null, $size = 'thumbnail', $icon = false, $attr = array() ){
            echo fifc_get_the_taxonomy_thumbnail( $term_id, $size, $icon, $attr );
        }
?>