cordova android app in the background crashes when a notification arrives

the app crashes when the I send a notification in background mode. This is the stack trace:

Thread [<23> Thread-1429] (Suspended (exception NullPointerException))
<VM does not provide monitor information>
NotificationMessageHandler.onMessage(Context, Bundle) line: 40
Registrations$1.run() line: 149
Thread.run() line: 841