LaunchCheckoutFlow OnComplete never called if dialog is dismissed with oculus button on controller

[wa1do.b]

The checkout flow dialog can be dismissed by pressing the oculus / meta button on the controller. This brings the user back to the app but the `OnComplete` event is never triggered.

Oculus.Platform.IAP.LaunchCheckoutFlow(_productID).OnComplete((result) => {

    // we never get here if dialog is dismissed with meta/oculus button on controller

})

We would expect to receive callback with "user_canceled" error message.