Also set duration_manual to zero

Dockerfile

@@ -6,7 +6,7 @@ RUN npm install && \
 
 FROM python:3.10.9-alpine
 
-ENV VERSION_NUMBER 0.1.2-8-gb77089f
+ENV VERSION_NUMBER 0.1.2-9-g7842d6f
 ENV PROD 1
 
 RUN apk add \

src/web/tracker/migrations/0006_auto_20230109_1904.py

@@ -0,0 +1,34 @@
+# Generated by Django 4.1.5 on 2023-01-09 18:04
+
+from django.db import migrations
+from datetime import timedelta
+
+
+def set_duration_manual_none_to_zero(apps, schema_editor):
+    Session = apps.get_model("tracker", "Session")
+    for session in Session.objects.all():
+        if session.duration_calculated == None:
+            session.duration_calculated = timedelta(0)
+            session.save()
+
+
+def revert_set_duration_manual_none_to_zero(apps, schema_editor):
+    Session = apps.get_model("tracker", "Session")
+    for session in Session.objects.all():
+        if session.duration_calculated == timedelta(0):
+            session.duration_calculated = None
+            session.save()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("tracker", "0005_auto_20230109_1843"),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            set_duration_manual_none_to_zero,
+            revert_set_duration_manual_none_to_zero,
+        )
+    ]