NPE在应用内购买

Question

这是我的代码，尝试在按下按钮时启动应用内购买：

purchaseButton.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View v) {

           if(purchased.equals("remove_ads")) {
               Toast.makeText(getApplicationContext(), "You already own the item.",
                       Toast.LENGTH_LONG).show();
           }
           else{

               try{

                   Bundle buyIntentBundle = mservice.getBuyIntent(3, getPackageName(),
                           "remove_ads", "inapp", "key");
                   PendingIntent pendingIntent = buyIntentBundle.getParcelable("BUY_INTENT");

                   try{
                       startIntentSenderForResult(pendingIntent.getIntentSender(), ///NPE here
                               1001, new Intent(), Integer.valueOf(0), Integer.valueOf(0),
                               Integer.valueOf(0));
                   }
                   catch(IntentSender.SendIntentException ee){
                       Toast.makeText(getApplicationContext(), "Error was: " + ee,
                               Toast.LENGTH_LONG).show();
                   }
                   catch(NullPointerException n){
                       Toast.makeText(getApplicationContext(), "Error was: " + n,
                               Toast.LENGTH_LONG).show();
                   }
               }
               catch (RemoteException e){
                   Toast.makeText(getApplicationContext(), "Error was: " + e,
                           Toast.LENGTH_LONG).show();
                   mHelper.flagEndAsync();

                   mHelper.launchPurchaseFlow(store.this, "remove_ads", 10001,
                           mPurchaseFinishedListener, "key");
               }
           }
       }
   });

由于某种原因，我在指示startIntentSenderForResult...的行上获得了NPE，但我不明白可能导致它的原因。以前我在应用程序购买中使用此代码完全如所示，除了它是一个不同的sku。它是否会有所不同，因为我在同一个类中显示了此代码块的2个相同副本？ Stacktrace也没有显示任何有用的东西，只有NPE。