title: NSURL for telephone always nil
body: <p>This is my <code>NSURL</code></p>
  
  <pre><code>let url = NSURL(string: "tel://\(phoneCall)")
  </code></pre>
  
  <p>It is always <code>nil</code>, although the <code>phoneCall</code> is a valid mobile number string, and I am testing on a real iPhone.</p>
  
  <p>I tried </p>
  
  <pre><code>let url = NSURL(string: "tel:\(phoneCall)")
  </code></pre>
  
  <p>but it's still <code>nil</code>.</p>