iOS 13.2 in app purchase dialog not appearing

### Platform

- [x] iOS
- [ ] macOS
- [ ] tvOS

### In-app purchase type

- [ ] Consumable
- [x] Non-consumable
- [ ] Auto-Renewable Subscription
- [ ] Non-Renewing Subscription

### Environment

- [x] Sandbox
- [ ] Production

### Version
0.15.0

## Report

### Issue summary
On iOS 13.2 purchase never call the completion closure, in-app purchase dialog is never shown.
The same code on iOS 13.1 works like a charm, the app tested on iOS 13.1 was rejected from the app store, for this reason, the reviewer tested on iOS 13.2.

ProductsInfoController.swift
```
for completion in query.completionHandlers {
completion(results) //do nothing
}
```

### Related issue
#500 something bad happen on iOS 13.2

### What did you expect to happen
the purchase should call the completion block and show the purchase dialog

### What happened instead
purchase dialog not shown