change author can also be null

src/c3nav/editor/migrations/0002_auto_20170612_1615.py

@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.2 on 2017-06-12 16:15
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('editor', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='change',
+            name='author',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT, related_name='changes', to=settings.AUTH_USER_MODEL, verbose_name='Author'),
+        ),
+    ]