allow journal to have no alternatives

scipost_django/journals/migrations/0137_alter_journal_alternative_journals.py

+# Generated by Django 4.2.15 on 2024-09-20 09:27
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("journals", "0136_publication_author_info_source"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="journal",
+            name="alternative_journals",
+            field=models.ManyToManyField(blank=True, to="journals.journal"),
+        ),
+    ]

scipost_django/journals/models/journal.py

@@ -145,7 +145,7 @@ class Journal(models.Model):
         blank=True,
     )
 
-    alternative_journals = models.ManyToManyField("self")
+    alternative_journals = models.ManyToManyField("self", blank=True)
 
     # Cost per publication information
     cost_info = models.JSONField(default=cost_default_value)