django.db.utils.IntegrityError: NOT NULL constraint failed: django_gamification_badge.next_badge_id

[caseynisu]

When i try to create new badge definition with the provided documentation of this project it raises Integrity Error.
Code i used:

from django_gamification.models import BadgeDefinition, Category
BadgeDefinition.objects.create(
name='Badge of Awesome',
description='You proved your awesomeness',
points=50,
progression_target=100,
category=Category.objects.create(name='Gold Badges', description='These are the top badges'),
)

Solution for this problem would be adding null=True on field next_badge of model Badge.