title: data parameter is nil error when checking internet connectivity
body: <p>When launching my app it checks if user is subscribed.  If it dosent detect an internet connection it crashes with the error:  </p>
  
  <p><code>Failed to retrieve subscription with error 'The Internet connection appears to be offline.' and responseString: (null)*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'data parameter is nil'
  </code></p>
  
  <p>.m</p>
  
  <pre><code>  [self getPath:path
     parameters:parameters
        success:^(AFHTTPRequestOperation *operation, id responseObject) {
            if (![responseObject isKindOfClass:[NSDictionary class]])
            {
                failureBlock(@"Invalid response received");
                return;
            }
            NSDictionary *responseDict = (NSDictionary *)responseObject;
            if (responseDict[@"error"] == nil)
            {
                [self saveUserDict:responseDict];
                successBlock(responseDict);
            }
            else
            {
                failureBlock(responseDict[@"error"]);
            }
        }
        failure:^(AFHTTPRequestOperation *operation, NSError *error) {
            DebugLog(@"Failed to log in with error '%@' and response: %@", error.localizedDescription, operation.responseString);
            failureBlock(@"An unknown error occurred");
        }];
  
   }
  
  
  
   - (void)getSubscriptionWithSuccessBlock:(void (^)(NSDictionary *subscriptionDict))successBlock
                         failureBlock:(void (^)(id responseObject))failureBlock
   {
  static NSString *path = @"/api/subscription";
  
  NSDictionary *parameters = @{
      @"userId" : userDict[@"userId"],
      @"token" : userDict[@"token"]
  };
  
   DebugLog(@"Getting subscription with parameters: %@", parameters);
  
  
  
       [self getPath:path
       parameters:parameters
        success:^(AFHTTPRequestOperation *operation, id responseObject) {
            if (![responseObject isKindOfClass:[NSDictionary class]])
            {
                failureBlock(@"Invalid response received");
                return;
            }
            NSDictionary *subscriptionDict = (NSDictionary *)responseObject;
            if (subscriptionDict[@"error"] == nil)
            {
                DebugLog(@"Successfully retrieved subscription");
                successBlock(subscriptionDict);
            }
            else
            {
                failureBlock(responseObject);
            }
        }
        failure:^(AFHTTPRequestOperation *operation, NSError *error) {
            DebugLog(@"Failed to retrieve subscription with error '%@' and responseString: %@", error.localizedDescription, operation.responseString);
            id responseObject = [NSJSONSerialization JSONObjectWithData:operation.responseData
                                                                options:0
                                                                  error:nil];
            failureBlock(responseObject);
        }];
      }
  </code></pre>