title: Web2py display "None", and I want to display nothing
body: <p>If I got an empty value from my database, web2py display "None" and I would like to display just a blank space (or nothing).
  Note: I do not need to change anything on the database value, just on the resulting display.</p>
  
  <p>I am using SQLFORM.smartgrid and getting the following:</p>
  
  <ul>
  <li>column1: 35.75  </li>
  <li>column2: None</li>
  <li>column3: 12.65</li>
  </ul>
  
  <p>I would like to display:</p>
  
  <ul>
  <li>column1: 35.75</li>
  <li>column2:</li>
  <li>column3: 12.65</li>
  </ul>
  
  <p>How can I do this?</p>
  
  <p>Thank you in advance for your help.
  Jose.</p>