App crashes in Low network like(EDGE,100 %loss) - ios

Question

My application implementing in-app purchase app crashes when connected to EDGE network, 100% loss,very poor network .There is no crash log. But it says "EXC BAD ACCESS code=1 address=0xc " on following line
_completionHandler(YES, skProducts);
Code for the method
#pragma mark - SKProductsRequestDelegate
- (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response {
sharedManager=[Mymanager sharedManager];
_productsRequest = nil;
sharedManager.bookidList=[[NSMutableArray alloc]init];
sharedManager.sharedProductPrice=[[NSMutableArray alloc]init];
NSArray * skProducts = response.products;
NSLog(#"sk product %#",skProducts);
// NSMutableArray *a=[[NSMutableArray alloc]init];
for (SKProduct * skProduct in skProducts) {
[sharedManager.sharedProductPrice addObject:skProduct.price];
[sharedManager.bookidList addObject:skProduct.productIdentifier];
}
[self updatePlist];
_completionHandler(YES, skProducts); //EXC BAD ACCESS CODE =1 ADDRESS=0XC
_completionHandler = nil;
}
I am following the in-app purchase tutorial on Ray Wenderlich's site (for iOS6.0). Minimum target of my application is iOS5. Any pointers how to fix this crash?
EDIT
New changes ,i made the NSArray to strong ARC property adn it still crashing check below images
tutorial
method to retrieve the product information from iTunes Connect:
- (void)requestProductsWithCompletionHandler:(RequestProductsCompletionHandler)completionHandler {
// 1
_completionHandler = [completionHandler copy];
// 2
_productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:_productIdentifiers];
_productsRequest.delegate = self;
[_productsRequest start];
}
This first squirrels a copy of the completion handler block inside the instance variable so it can notify the caller when the product request asynchronously completes.
It then creates a new instance of SKProductsRequest, which is the Apple-written class that contains the code to pull the info from iTunes Connect. It’s very easy to use – you just give it a delegate (that conforms to the SKProductsRequestDelegate protocol) and then call start to get things running.
We set the IAPHelper class itself as the delegate, which means that it will receive a callback when the products list completes (productsRequest:didReceiveResponse) or fails (request:didFailWithErorr).
Speaking of delegate callbacks, add those next! Add the following code before the #end:

Answer 1

It's quite likely that _completionHandler is nil when you are calling it in the method above. Attempting to execute a block variable when the variable is nil does give a bad access error.
You can confirm this by wrapping the execution of the completion handler block in an if statement and only executing it if the variable isn't nil:
if(_completionHandler)
{
_completionHandler(YES, skProducts);
}
Fixing the problem is another matter, you would need to trace the calls and see when the completion block is either not passed or removed.