title: "Cannot read property addEventListener of null" when adding EventListener JavaScript
body: <p>I am trying to add an eventListener to a variable set to an element. 
  The code is this:</p>
  
  <pre><code>var c = document.getElementById("some_element");
  c.addEventListener("click", someFunction);
  </code></pre>
  
  <p>(BTW if it helps the element is a <strong>button</strong>.) </p>