In App Purchase crashes in Android 4.4

Android Android Development
1

Hi,
I use the IAP helper class in the first activity of an app, to check if someone did a purchase. Everything works well generally, except a few crashes. I notice that all crashes with Android 4.4 devices, and they are Null Pointer exceptions.

I get this exception, only in 4.4 devices:

java.lang.NullPointerException
at nl.myDeveloperName.appName.util.IabHelper.queryPurchases(IabHelper.java:836)
at nl.myDeveloperName.appName.util.IabHelper.queryInventory(IabHelper.java:558)
at nl.myDeveloperName.appName.util.IabHelper.queryInventory(IabHelper.java:522)
at nl.myDeveloperName.appName.util.IabHelper$2.run(IabHelper.java:617)
at java.lang.Thread.run(Thread.java:841)

So I assume IabHelper could not instantiate as object. But why?