default value for pd_family set to NULL

smash/web/migrations/0039_pd_family_default_unknown.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.7 on 2017-05-17 13:46
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('web', '0038_subject_pd_family_allow_null'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='subject',
+            name='pd_in_family',
+            field=models.NullBooleanField(default=None, verbose_name=b'PD in family'),
+        ),
+        migrations.RunSQL(
+            "UPDATE web_subject SET pd_in_family=NULL WHERE pd_in_family = FALSE;",
+            reverse_sql="UPDATE web_subject SET pd_in_family=FALSE WHERE pd_in_family = NULL;")
+    ]

smash/web/models/subject.py

@@ -149,7 +149,7 @@ class Subject(models.Model):
     )
     pd_in_family = models.NullBooleanField(
         verbose_name='PD in family',
-        default=False,
+        default=None,
     )
     dead = models.BooleanField(
         verbose_name='Deceased',