manytomany filter horizontal didn't work django admin

Question

Getting below error while add a field in LabelLink model Currently I am working on django-cms and want to change current admin widget.

IntegrityError at /admin/myapp/labellinkmodel/add/ NOT NULL constraint failed: myapp_labellink_links.sort_value

models.py

class LinkPluginModel(CMSPlugin):
    .....
    label = models.CharField(max_length=200)
    link = models.URLField()


class LabelLink(CMSPlugin):
    ...
    links = models.ManyToManyField(LinkPluginModel,related_name="links" ,blank=True)

admin.py

class LabelLinkAdmin(admin.ModelAdmin):
    filter_horizontal = ('links',)

admin.site.register(LabelLink,LabelLinkAdmin)

Answer 1

create a forms.py and add this code. It will definitely solve your problem.

class LabelLinkForm(ModelForm):

  class Meta:
    model = Model Name
    fields="__all__"

  def __init__(self, *args, **kwargs):
    super(LabelLinkForm, self).__init__(*args, **kwargs)
    self.fields['links'].required = False