title: Get None from a Fields data in instead of an empty string
body: <p>I have this field in the <code>WTForms</code> form</p>
  
  <pre><code>name = StringField('Name', validators = [Optional(), Length(max = 100)])
  </code></pre>
  
  <p>When the field is submitted empty then <code>form.name.data</code> will, as expected, contain an empty string.</p>
  
  <p>Is there some way to make it return <code>None</code> in instead of an empty string? It is just because it is very convenient to deal with <code>null</code> in the database like in this <code>update</code>:</p>
  
  <pre><code>update t
  set 
      name = coalesce(%(name)s, name),
      other = coalesce(%(other)s, other)
  </code></pre>
  
  <p>With the above code I don't need to check if the field is empty or not and take actions accordingly be it in the Python code on in the SQL code. The <code>null</code> with the <code>coalesce</code> solves that easily.</p>