undefined is not iterable on mongoDB backend
I'm encountering this error from time to time:

```
undefined` is not iterable (cannot read property Symbol(Symbol.iterator)) TypeError: undefined is not iterable (cannot read property Symbol(Symbol.iterator))
    at RateLimiterMongo._getRateLimiterRes (C:\www\projects\uefa_app\node_modules\rate-limiter-flexible\lib\RateLimiterMongo.js:117:15)
    at RateLimiterMongo._afterConsume (C:\www\projects\uefa_app\node_modules\rate-limiter-flexible\lib\RateLimiterStoreAbstract.js:51:22)
    at C:\www\projects\uefa_app\node_modules\rate-limiter-flexible\lib\RateLimiterStoreAbstract.js:205:16
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
```

https://github.com/animir/node-rate-limiter-flexible/blob/184d1d883583c53a5aff47726bc10afb6de3e4e9/lib/RateLimiterMongo.js#L116

Originally the issue seems to come from Mongo driver 4 as they have [removed the ops attribute](https://github.com/mongodb/node-mongodb-native/blob/4.0/HISTORY.md#-breaking-changes-1), needed when [using replaceOne](https://github.com/animir/node-rate-limiter-flexible/blob/184d1d883583c53a5aff47726bc10afb6de3e4e9/lib/RateLimiterMongo.js#L211)