Closes #17761: Store empty CharField choices as null

netbox/tenancy/migrations/0016_charfield_null_choices.py

@@ -0,0 +1,29 @@
+from django.db import migrations, models
+
+
+def set_null_values(apps, schema_editor):
+    """
+    Replace empty strings with null values.
+    """
+    ContactAssignment = apps.get_model('tenancy', 'ContactAssignment')
+
+    ContactAssignment.objects.filter(priority='').update(priority=None)
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('tenancy', '0015_contactassignment_rename_content_type'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='contactassignment',
+            name='priority',
+            field=models.CharField(blank=True, max_length=50, null=True),
+        ),
+        migrations.RunPython(
+            code=set_null_values,
+            reverse_code=migrations.RunPython.noop
+        ),
+    ]