Android : In App Purchased restore in Android v3?

I have two buttons in my android code one is buy and second is Restore. I have success with the buy a product via in app purchased, but when i use restore button to restore my transaction in my signed apk file. It will crash when i press the restore button. Here is my code on both button's action:

Buy button on click :

if(BillingHelper.isBillingSupported()){
                BillingHelper.requestPurchase(getApplicationContext(), inappId); 

            } else {
                BuyBtn.setEnabled(false);
            }

ResoreBtn on click :

                BillingHelper.restoreTransactionInformation(BillingSecurity.generateNonce());

Please help me regarding restore transaction in android.