NullPointerException back from CheatActivity


I’m not able to face the Challenges as I get a NullPointerException after tapping the back button from CheatActivity after having clicked on ShowAnswer and having Ctrl+F12 (rotate the screen).
Initially I thought it was me not having wrote correctly all the code teached in Chapter 5, so I have tried to load in Eclipse the Book’s solutions downloaded from your site (created a new project from existing folders) and the same issue is happening.
Short log from LogCat:

11-13 07:39:36.891: E/AndroidRuntime(1683): FATAL EXCEPTION: main
11-13 07:39:36.891: E/AndroidRuntime(1683): java.lang.RuntimeException: Unable to resume activity {}: java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=0, result=0, data=null} to activity {}: java.lang.NullPointerException

Any hint how to solve it?
Testing on:
Eclipse 4.2
Android SDK 4.3
java version "1.7.0_07"
Java™ SE Runtime Environment (build 1.7.0_07-b11)
Java HotSpot™ 64-Bit Server VM (build 23.3-b01, mixed mode)
win7 64 bit



I’m having the exact same problem except for me it happens when I rotate the device (galaxy tab 3) after hitting show answer. Any thoughts would be much appreciated.