title: Hide None value of django form field
body: <p>I have a end_date field on my news apps which is a facultative field.
  When a author is editing one of his new and erase the end_date, I set in the model the end_date to None.</p>
  
  <p>My problem is that the field then display the value 'None' on next edit instead of just being blank.</p>
  
  <p>Here is my field :</p>
  
  <p><strong>models.py</strong></p>
  
  <pre><code>end_date = models.DateTimeField(null=True, blank=True)
  </code></pre>
  
  <p><strong>forms.py</strong></p>
  
  <pre><code>end_date = forms.CharField(label='', required=False, widget=forms.DateTimeInput(attrs={'class': 'form-control', 'format': 'DD, d MM yy', 'placeholder': _('End date')}))
  </code></pre>
  
  <p>and the assignation in my view :</p>
  
  <p><strong>views.py</strong></p>
  
  <pre><code> if news_form.cleaned_data['end_date'] == '' :
      edited_new.end_date = None 
   edited_new.save()
  </code></pre>
  
  <p>EDIT : </p>
  
  <p>here is my template :</p>
  
  <p><strong>news.html</strong></p>
  
  <pre><code>        &lt;form action="#" method="post" role="form" id="news-form"&gt;{% csrf_token %}
          {{ news_form.media }}
          &lt;div class="col-xs-12"&gt;
              &lt;div class="panel panel-primary"&gt;
                  &lt;div class="panel-heading"&gt;
                      &lt;div class="row"&gt;
                          &lt;div class="col-xs-12 col-md-6"&gt;
                              &lt;h2 class="panel-title"&gt;{% trans "Add or edit news" %}&lt;/h2&gt;
                          &lt;/div&gt;
                          &lt;div class="col-xs-12 col-md-6"&gt;
                              &lt;div class="pull-right"&gt;
                                  &lt;a href="#" class="btn btn-secondary cancel"&gt;&lt;span class="glyphicon glyphicon-floppy-remove"&gt;&lt;/span&gt; {% trans "Cancel" %}&lt;/a&gt;
                                  &lt;button type="submit" class="btn btn-primary form-btn save"&gt;&lt;span class="glyphicon glyphicon-floppy-saved"&gt;&lt;/span&gt;&lt;span class="button-text"&gt; {% trans "Save" %}&lt;/span&gt;&lt;/button&gt;
                              &lt;/div&gt;
                          &lt;/div&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
                  &lt;div class="panel-body"&gt;
                      &lt;div class="row"&gt;
                          &lt;div class="col-xs-12 col-md-6"&gt;
                              {{ news_form.title }}
                          &lt;/div&gt;
                          &lt;div class="col-xs-4 col-md-2"&gt;
                              {% trans 'Tag' %}
                          &lt;/div&gt;
                          &lt;div class="col-xs-8 col-md-4"&gt;
                              {{ news_form.tag }}
                          &lt;/div&gt;
                      &lt;/div&gt;
                      &lt;div class="row"&gt;
                          &lt;div class="col-xs-12 no-label-field redactor-field"&gt;
                              {{ news_form.message }}
                          &lt;/div&gt;
                      &lt;/div&gt;
                      &lt;div class="row"&gt;
                          &lt;div class="col-xs-6 date-field no-label-field"&gt;
                              &lt;div class="form-group"&gt;
                                  &lt;div class='input-group date datetimepicker'&gt;
                                      {{ news_form.start_date }}
                                      &lt;span class="input-group-addon"&gt;&lt;span class="glyphicon glyphicon-calendar"&gt;&lt;/span&gt;
                                      &lt;/span&gt;
                                  &lt;/div&gt;
                              &lt;/div&gt;
                          &lt;/div&gt;
                          &lt;div class="col-xs-6 date-field no-label-field"&gt;
                              &lt;div class="form-group"&gt;
                                  &lt;div class='input-group date datetimepicker'&gt;
                                      {{ news_form.end_date }}
                                      &lt;span class="input-group-addon"&gt;&lt;span class="glyphicon glyphicon-calendar"&gt;&lt;/span&gt;
                                      &lt;/span&gt;
                                  &lt;/div&gt;
                              &lt;/div&gt;
                          &lt;/div&gt;
                      &lt;/div&gt;
                      &lt;div class="row"&gt;
                          &lt;div class="col-xs-12"&gt;
                              {{ news_form.active }} {% trans 'Activate the news' %}
                          &lt;/div&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
          &lt;/div&gt;
          &lt;span style="display:none;"&gt;{{ news_form.id }}&lt;/span&gt;
      &lt;/form&gt;
  </code></pre>