title: get_the_post_thumbnail_url() not working when adding an image size
body: <p>I have a weird situation when I am trying to use <code>get_the_post_thumbnail_url()</code> in Wordpress.</p>
  
  <p>To be more precise, I have this variable:</p>
  
  <pre><code>$postImage = get_the_post_thumbnail_url('article-thumbnail-image');
  </code></pre>
  
  <p>and it returns a blank value. If I use:</p>
  
  <pre><code>$postImage = get_the_post_thumbnail_url();
  </code></pre>
  
  <p>the value returned is correct but it has a different image size (150x150). Now the weird part is if I use:</p>
  
  <pre><code>the_post_thumbnail_url('article-thumbnail-image');
  </code></pre>
  
  <p>it shows the right value as this image size is registered in <code>functions.php</code> but I need to use the GET function.</p>
  
  <p>Am I doing something wrong?</p>