title: Cast to Boolean failed for value "on" path "sell"
body: <p>Currently I'm having this strange error this have never happened to me before. When I post a form with checked checkbox "sale" I get this error <code>Cast to Boolean failed for value "on" path "sell"</code>
  This is the schema part from model: </p>
  
  <pre><code>    sell: {
      type: Boolean,
      default: false
      },
  </code></pre>
  
  <p>This is how I request the checkbox:</p>
  
  <pre><code>sell: req.body.sell
  </code></pre>
  
  <p>And then I save everything but I get that error. Maybe there's better logic than this to check if checkbox was checked ? </p>