光滑的滑块RTL不起作用，但LTR起作用

Question

标题是不言自明的，此滑块不能用于RTL，只能用于LTR，为什么？

jQuery( document ).ready( function( $ ) {
  $( '.slick-slider-media' ).slick( {
    slidesToShow: 3,
    slidesToScroll: 1,
    autoplay: true,
    arrows: true,
    prevArrow: '<button type="button" class="slick-prev"><i class="fa fa-chevron-right" aria-hidden="true"></i></button>',
    nextArrow: '<button type="button" class="slick-next"><i class="fa fa-chevron-left" aria-hidden="true"></i></button>',
    dots: false,
    rtl: true,
  } );
} );

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/slick-carousel/1.9.0/slick.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/slick-carousel/1.9.0/slick.min.css" />
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/slick-carousel/1.9.0/slick-theme.min.css" />
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css" />
<div class="slick-slider-media">
  <div><img src="http://cdn.24.co.za/files/Cms/General/d/7754/5df80300f5b740d0a4bd1d6ce30f9a1c.jpg" alt="" /></div>
  <div><img src="http://cdn.24.co.za/files/Cms/General/d/7754/5df80300f5b740d0a4bd1d6ce30f9a1c.jpg" alt="" /></div>
  <div><img src="http://cdn.24.co.za/files/Cms/General/d/7754/5df80300f5b740d0a4bd1d6ce30f9a1c.jpg" alt="" /></div>
  <div><img src="http://cdn.24.co.za/files/Cms/General/d/7754/5df80300f5b740d0a4bd1d6ce30f9a1c.jpg" alt="" /></div>
  <div><img src="http://cdn.24.co.za/files/Cms/General/d/7754/5df80300f5b740d0a4bd1d6ce30f9a1c.jpg" alt="" /></div>
  <div><img src="http://cdn.24.co.za/files/Cms/General/d/7754/5df80300f5b740d0a4bd1d6ce30f9a1c.jpg" alt="" /></div>
</div>

谢谢