Add simple null checks to StorageWizard*, also listen to...

the disk destroyed event.

Bug 21336042

Change-Id: I9f53501a6122a4a9046774e3c4c08b5d6d6f8552

src/com/android/settings/deviceinfo/StorageWizardMigrate.java

@@ -35,10 +35,12 @@ public class StorageWizardMigrate extends StorageWizardBase {
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
+        if (mDisk == null) {
+            finish();
+            return;
+        }
         setContentView(R.layout.storage_wizard_migrate);
 
-        Preconditions.checkNotNull(mDisk);
-
         setHeaderText(R.string.storage_wizard_migrate_title, mDisk.getDescription());
         setBodyText(R.string.memory_calculating_size);