Use blank=True for voters

elections/migrations/0010_blank_voters.py

@@ -0,0 +1,28 @@
+# Generated by Django 2.2.19 on 2021-03-18 13:48
+
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("elections", "0009_auto_20210318_1441"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="election",
+            name="voters",
+            field=models.ManyToManyField(
+                blank=True, related_name="cast_elections", to=settings.AUTH_USER_MODEL
+            ),
+        ),
+        migrations.AlterField(
+            model_name="question",
+            name="voters",
+            field=models.ManyToManyField(
+                blank=True, related_name="cast_questions", to=settings.AUTH_USER_MODEL
+            ),
+        ),
+    ]