Initialize fake WorkerVersion with non-empty configuration

arkindex/dataimport/management/commands/fake_worker_version.py

@@ -63,7 +63,7 @@ class Command(BaseCommand):
         version = WorkerVersion.objects.create(
             worker=worker,
             revision=revision,
-            configuration="",
+            configuration={"configuration": {}},
         )
 
         logger.info(f"Created a worker version: {version.id}")