title: Django DecimalField returns "None" instead of empty value
body: <p>Is there a way to force django to display nothing instead of "None" for a Decimal Field that's been left blank?  </p>
  
  <p>In my template, I show a list of all the values for a particular field.  Each value is hyperlinked to a page that displays the results of a query filtered on that value.  But because there are some entries with null value, my list includes actual DecimalField entries and "None" for all those that are empty.  When a user clicks on None, django throws a validation error because you cannot query a DecimalField using a string.  </p>
  
  <p>I could write if statements checking all instances of decimal fields for Nones and skipping them, but that is far from an elegant solution.  Any advice?</p>
  
  <p>This is one part of the code, though there are other templates that derive the None value in slightly different manners:</p>
  
  <pre><code>{% for item in choices %}
      &lt;a href={% url app_views.field_choice item %}&gt;{{ item }}&lt;/a&gt;&lt;br&gt;
  {% endfor %}
  </code></pre>