title: asNavFor not working ngx-slick-carousel in Angular 8
body: <p>I am working on a project made in Angular 8 &amp; want to use a third-party library such as <a href="https://www.npmjs.com/package/ngx-slick-carousel" rel="nofollow noreferrer">ngx-slick-carousel</a> and everything is working fine but I have thumbnail carousel, where an option like <code>asNavFor</code>, see the below attributes </p>
  
  <pre><code>imagesSlider = {
    speed:300,
    slidesToShow:1,
    slidesToScroll:1,
    cssEase:'linear',
    fade:true,
    autoplay: true,
    draggable:true,
    prevArrow:'.client-feedback .prev-arrow',
    nextArrow:'.client-feedback .next-arrow',
    asNavFor:".client-thumbnails",
  };
  thumbnailsSlider = {
    speed:300,
    slidesToShow:5,
    slidesToScroll:1,
    cssEase:'linear',
    autoplay: true,
    centerMode:true,
    draggable:false,
    focusOnSelect:true,
    asNavFor:".feedback-slides .client-feedback",
    prevArrow:'.client-thumbnails .prev-arrow',
    nextArrow:'.client-thumbnails .next-arrow',
  };
  </code></pre>
  
  <p>and the HTML looks like </p>
  
  <pre><code>&lt;div class="feedback-slides"&gt;
     &lt;div class="client-feedback"&gt;
          &lt;ngx-slick-carousel 
              class="carousel" 
              #slickModal="slick-carousel" 
              [config]="imagesSlider"&gt;
              &lt;div ngxSlickItem *ngFor="let slide of slides" class="slide"&gt;
                      &lt;img src="{{ slide.img }}" alt="" width="100%"&gt;
              &lt;/div&gt;
          &lt;/ngx-slick-carousel&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  
  &lt;div class="client-thumbnails"&gt;
       &lt;ngx-slick-carousel 
          class="carousel" 
          #slickModal="slick-carousel" 
          [config]="thumbnailsSlider "&gt;
          &lt;div ngxSlickItem *ngFor="let slide of slides" class="slide"&gt;
                  &lt;img src="{{ slide.img }}" alt="" width="100%"&gt;
          &lt;/div&gt;
      &lt;/ngx-slick-carousel&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>as above codes not working &amp; showing an error in the console like </p>
  
  <blockquote>
    <p>Uncaught TypeError: Cannot read property 'getSlick' of undefined</p>
  </blockquote>
  
  <p>If I remove the option <code>asNavFor</code> error will disappear but thumb click doesn't work anymore.</p>
  
  <p>What can I do now?</p>
  
  <p>Thanks</p>