title: How to check that shortcode is empty in wordpress
body: <p>I am using the WooCommerce plugin. I created a sale page and use <code>[sale_products]</code> shortcode of WooCommerce. It shows me all sales product perfectly, now I want that if there are no sale products, the message will be show "there is no sale product".</p>
  
  <p>Like this:</p>
  
  <pre><code>if(!empty([sale_products])) {
      [sale_products]
  } else {
      // message
  }
  </code></pre>
  
  <p>Is there any way to handle this?</p>