Fix typo

server/migrations.js

@@ -1077,7 +1077,7 @@ Migrations.add('change-attachment-library', () => {
 		}
 		Attachments.addFile(path, opts, (err, fileRef) => {
       if (err) {
-        console.log('error when migrating ', fileName, err);
+        console.log('error when migrating ', fileRef.name, err);
       }
     });
 	});