FATAL EXCEPTION: main
                                                   Process: com.example.android.persistence, PID: 27437
                                                   java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.persistence/com.example.android.persistence.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Package.getName()' on a null object reference
                                                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2984)
                                                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045)
                                                       at android.app.ActivityThread.-wrap14(ActivityThread.java)
                                                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642)
                                                       at android.os.Handler.dispatchMessage(Handler.java:102)
                                                       at android.os.Looper.loop(Looper.java:154)
                                                       at android.app.ActivityThread.main(ActivityThread.java:6776)
                                                       at java.lang.reflect.Method.invoke(Native Method)
                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496)
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)
                                                    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Package.getName()' on a null object reference
                                                       at android.arch.lifecycle.Lifecycling.java.lang.reflect.Constructor getGeneratedAdapterConstructor(java.lang.Class)(Lifecycling.java:84)
                                                       at android.arch.lifecycle.Lifecycling.android.arch.lifecycle.GenericLifecycleObserver getCallback(java.lang.Object)(Lifecycling.java:60)
                                                       at android.arch.lifecycle.LifecycleRegistry$ObserverWithState.void <init>(android.arch.lifecycle.LifecycleRegistry,android.arch.lifecycle.LifecycleObserver)(LifecycleRegistry.java:198)
                                                       at android.arch.lifecycle.LifecycleRegistry.void addObserver(android.arch.lifecycle.LifecycleObserver)(LifecycleRegistry.java:108)
                                                       at android.arch.lifecycle.LiveData.void observe(android.arch.lifecycle.LifecycleOwner,android.arch.lifecycle.Observer)(LiveData.java:199)
                                                       at com.example.android.persistence.ProductListFragment.void subscribeUi(com.example.android.persistence.viewmodel.ProductListViewModel)(ProductListFragment.java:70)
                                                       at com.example.android.persistence.ProductListFragment.void onActivityCreated(android.os.Bundle)(ProductListFragment.java:65)
                                                       at android.support.v4.app.Fragment.void performActivityCreated(android.os.Bundle)(Fragment.java:2201)
                                                       at android.support.v4.app.FragmentManagerImpl.void moveToState(android.support.v4.app.Fragment,int,int,int,boolean)(FragmentManager.java:1326)
                                                       at android.support.v4.app.FragmentManagerImpl.void moveFragmentToExpectedState(android.support.v4.app.Fragment)(FragmentManager.java:1528)
                                                       at android.support.v4.app.FragmentManagerImpl.void moveToState(int,boolean)(FragmentManager.java:1595)
                                                       at android.support.v4.app.BackStackRecord.void executeOps()(BackStackRecord.java:758)
                                                       at android.support.v4.app.FragmentManagerImpl.void executeOps(java.util.ArrayList,java.util.ArrayList,int,int)(FragmentManager.java:2363)
                                                       at android.support.v4.app.FragmentManagerImpl.void executeOpsTogether(java.util.ArrayList,java.util.ArrayList,int,int)(FragmentManager.java:2149)
                                                       at android.support.v4.app.FragmentManagerImpl.void optimizeAndExecuteOps(java.util.ArrayList,java.util.ArrayList)(FragmentManager.java:2103)
                                                       at android.support.v4.app.FragmentManagerImpl.boolean execPendingActions()(FragmentManager.java:2013)
                                                       at android.support.v4.app.FragmentController.boolean execPendingActions()(FragmentController.java:388)
                                                       at android.support.v4.app.FragmentActivity.void onStart()(FragmentActivity.java:607)
                                                       at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1256)
                                                       at android.app.Activity.performStart(Activity.java:6972)
                                                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2937)
                                                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045) 
                                                       at android.app.ActivityThread.-wrap14(ActivityThread.java) 
                                                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642) 
                                                       at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                       at android.os.Looper.loop(Looper.java:154) 
                                                       at android.app.ActivityThread.main(ActivityThread.java:6776) 
                                                       at java.lang.reflect.Method.invoke(Native Method) 
                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496) 
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)