Todo-java8 crashing on orientation changes

[ar-g]

Here is stacktrace:

ATAL EXCEPTION: main
                                                                        java.lang.IllegalArgumentException: The observer is null.
                                                                            at android.database.Observable.unregisterObserver(Observable.java:64)
                                                                            at android.widget.BaseAdapter.unregisterDataSetObserver(BaseAdapter.java:42)
                                                                            at android.widget.AbsListView.onDetachedFromWindow(AbsListView.java:2608)
                                                                            at android.view.View.dispatchDetachedFromWindow(View.java:11972)
                                                                            at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2532)
                                                                            at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2530)
                                                                            at android.view.ViewGroup.removeViewsInternal(ViewGroup.java:3701)
                                                                            at android.view.ViewGroup.removeViews(ViewGroup.java:3583)
                                                                            at trikita.anvil.Anvil.unmount(Anvil.java:138)
                                                                            at trikita.anvil.RenderableView.onDetachedFromWindow(RenderableView.java:33)
                                                                            at android.view.View.dispatchDetachedFromWindow(View.java:11972)
                                                                            at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2532)
                                                                            at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2530)
                                                                            at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2530)
                                                                            at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2530)
                                                                            at android.view.ViewRootImpl.dispatchDetachedFromWindow(ViewRootImpl.java:2625)
                                                                            at android.view.ViewRootImpl.doDie(ViewRootImpl.java:4088)
                                                                            at android.view.ViewRootImpl.die(ViewRootImpl.java:4071)
                                                                            at android.view.WindowManagerGlobal.removeViewLocked(WindowManagerGlobal.java:336)
                                                                            at android.view.WindowManagerGlobal.removeView(WindowManagerGlobal.java:286)
                                                                            at android.view.WindowManagerImpl.removeViewImmediate(WindowManagerImpl.java:84)
                                                                            at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3487)
                                                                            at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3669)
                                                                            at android.app.ActivityThread.access$700(ActivityThread.java:141)
                                                                            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1240)
                                                                            at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                            at android.os.Looper.loop(Looper.java:137)
                                                                            at android.app.ActivityThread.main(ActivityThread.java:5041)
                                                                            at java.lang.reflect.Method.invokeNative(Native Method)
                                                                            at java.lang.reflect.Method.invoke(Method.java:511)
                                                                            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
                                                                            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
                                                                            at dalvik.system.NativeStart.main(Native Method)