title: Angular data binding returning NaN when value is zero
body: <p>I'm doing some simple data binding like so:</p>
  
  <pre><code>&lt;input type="text" class="form-control" model="amount"&gt;
  &lt;label&gt;Your amount is {{amount * 10 }}&lt;/label&gt;
  </code></pre>
  
  <p>However, initially, when the text input is empty it returns NaN.</p>
  
  <p>How can I prevent this from happening with Angular?</p>