Acf Pro repeater field returns null when call inside foreach

I found a Notice error in your code. You have used $description in your code.
Initially you have not defined it and directly using concatenation to it.

function label_text( $post_id = '' ) {
    $description = '';        
    while( have_rows('description', $post_id) ): the_row();
                    $description .= get_sub_field('label') . get_sub_field('text');
            endwhile;
    return $description;
}