title: touchesBegan not firing in PDFView
body: <p>I am trying to determine the location of a touch on a PDFView. I have set my pdf view to be user interacted as follows:</p>
  
  <pre><code>pdfView?.isUserInteractionEnabled = true
  </code></pre>
  
  <p>I then use the following function to detect touches:</p>
  
  <pre><code> override func touchesBegan(_ touches: Set&lt;UITouch&gt;, with event: UIEvent?) {
      if let touch = touches.first {
          let position = touch.location(in: pdfView)
          print(position)
      }
  }
  </code></pre>
  
  <p>The touchesBegan code is never fired.</p>