Fix MongoDB Backups failing!

app/Models/StandaloneMongodb.php

@@ -224,6 +224,6 @@ class StandaloneMongodb extends BaseModel
         return $this->morphMany(ScheduledDatabaseBackup::class, 'database');
     }
     public function database_name() {
-        return $this->mongo_db;
+        return "???";
     }
 }