messages: Mark is_channel_message as non-null.

zerver/migrations/0692_alter_message_is_channel_message.py

@@ -0,0 +1,20 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("zerver", "0691_backfill_message_is_channel_message"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="archivedmessage",
+            name="is_channel_message",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="message",
+            name="is_channel_message",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+    ]

zerver/models/messages.py

@@ -98,7 +98,7 @@ class AbstractMessage(models.Model):
     # Whether the message contains a link.
     has_link = models.BooleanField(default=False, db_index=True)
     # If the message is a channel message (as opposed to a DM or group-DM)
-    is_channel_message = models.BooleanField(default=True, null=True, db_index=True)
+    is_channel_message = models.BooleanField(default=True, db_index=True)
 
     class Meta:
         abstract = True