title: Django rest framework imagefield optional
body: <p>models.py</p>
  
  <pre><code>picture = models.ImageField(upload_to='Images/', 
                              default='/Images/None/No-img.jpg', blank=True,null=True)
  </code></pre>
  
  <p>serializers.py</p>
  
  <pre><code>class UserProfileSerializer(serializers.ModelSerializer):
      picture = serializers.ImageField(max_length=None, 
                                       allow_empty_file=True, use_url=True)
  
      class Meta:
          model = UserProfile
          fields = ('id','picture',)     
          read_only_fields=('id')
  </code></pre>
  
  <p>But it's still showing as a required field, I can't make post request with image, is it a bug?</p>