  
      if model_field.has_default() or model_field.blank or model_field.null:
          kwargs['required'] = False
  
      if model_field.null:
          kwargs['allow_null'] = True
  
      if model_field.blank and (isinstance(model_field, (models.CharField, models.TextField))):
          kwargs['allow_blank'] = True
  
      if not model_field.blank and (postgres_fields and isinstance(model_field, postgres_fields.ArrayField)):
          kwargs['allow_empty'] = False
 
</s> remove         if model_field.null:
            kwargs['allow_null'] = True
 </s> add 
  
      if model_field.has_default() or model_field.blank or model_field.null:
          kwargs['required'] = False
  



      if model_field.blank and (isinstance(model_field, (models.CharField, models.TextField))):
          kwargs['allow_blank'] = True
  
      if not model_field.blank and (postgres_fields and isinstance(model_field, postgres_fields.ArrayField)):
          kwargs['allow_empty'] = False
keep keep keep keep replace replace replace keep keep keep keep keep
 Make autogenerated read only fields to be able to be nullable (#8536) 
rest_framework/utils/field_mapping.py