NullPointerException RateMeMaybeFragment.onCancel()

[shkschneider]

java.lang.NullPointerException
at com.kopfgeldjaeger.ratememaybe.RateMeMaybeFragment.onCancel(RateMeMaybeFragment.java:74)
at android.app.Dialog$ListenersHandler.handleMessage(Dialog.java:1249)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5196)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
at dalvik.system.NativeStart.main(Native Method)