if ( ! function_exists( 'tvcnews_mce_css' ) ) {
    function tvcnews_mce_css( $mce_css ) {
        $css_url = get_stylesheet_directory_uri() . '/editor-fix.css';
        if ( ! empty( $mce_css ) ) {
            $mce_css .= ',' . $css_url;
        } else {
            $mce_css = $css_url;
        }
        return $mce_css;
    }
    add_filter( 'mce_css', 'tvcnews_mce_css' );
}