title: Django REST Framework: how to substitute null with empty string?
body: <p>I have a model with ImageField type below:</p>
  
  <pre><code>class Attendance(models.Model):
      face_image = models.ImageField(, blank=True, null=True, storage=MediaStorage())
  </code></pre>
  
  <p>A serializer that is based on the model</p>
  
  <pre><code>class AttendanceSerializer(serializers.ModelSerializer):
  
      class Meta:
          model = Attendance
          fields = ('id','face_image')
  </code></pre>
  
  <p>However if the imagefield is null, it shows like this</p>
  
  <pre><code>Its now showing like this in the json
  
    {
      "id": 1,
      "face_image": null
    }
  </code></pre>
  
  <p>It will show an output for face_image (ImageField) as null if it is None. What I would like is to substitute null to be an empty string like this ""</p>