title: Trigger click not working
body: <p>Edit:
  Thank you so much for all the effort, got all my code running now!</p>
  
  <p>I want to trigger a click on <a href="https://shop.adidas.ae/en/stan-smith-shoes/S82255.html" rel="nofollow noreferrer">https://shop.adidas.ae/en/stan-smith-shoes/S82255.html</a> (to make a shoe bot).
  Why does this code not work to trigger the size type button?</p>
  
  <pre><code>setTimeout(function () {
     $('select.product-type.js-size-type').trigger('click');
  }, 1000);
  </code></pre>
  
  <p>This is the select button:</p>
  
  <pre><code>&lt;select class="product-type js-size-type"&gt;
  </code></pre>
  
  <p>This is what chrome console says</p>
  
  <pre><code>caught TypeError: Cannot read property 'click' of null
      at &lt;anonymous&gt;:2:41
  </code></pre>
  
  <p><em>Updated:</em></p>
  
  <p>My manifest of the chrome extension:</p>
  
  <pre><code>{
    "name": "name",
    "description": "test",
    "version": "1.0",
    "manifest_version": 2,
    "permissions": ["*://*/*"],
    "content_scripts": [
      {
        "matches": ["*://*.adidas.ae/*"],
        "js": ["jquery.js", "yeezyCopper.js"]
      }
    ],
    "background": {
      "scripts": ["background.js"],
      "persistent": false
    }
  }
  </code></pre>
  
  <p>YeezyCopper.js :</p>
  
  <pre><code>setTimeout(function () {
     $('select.product-type.js-size-type').trigger('click');
  }, 1000);
  </code></pre>
  
  <p>Thanks in advance!</p>