Intermittent no‑callback issue for SKProductsRequest

Occasionally there is no delegate callback when invoking the StoreKit API below.

```objc

SKProductsRequest * productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:_productsIdSet];

productsRequest.delegate = self;

[productsRequest start];

```

## Expected behavior

Should receive callback from `SKProductsRequestDelegate` either on success or failure.

## Actual behavior

Sometimes neither `productsRequest:didReceiveResponse:` nor `requestDidFinish:` / `request:didFailWithError:` gets triggered, no callback arrives.

## Environment

- iOS StoreKit In‑App Purchase

- Occasional / intermittent issue, cannot reproduce 100%

## Suspected root causes

1. `SKProductsRequest` instance gets deallocated prematurely before request completes.

2. Unstable network or Apple Store server latency.

3. Sandbox account anomaly on test devices.