Read disk ID from intent

mDisk might be null, but we can recover the disk ID from the original
Intent.

Bug: 28177789
Change-Id: Ic3e33a60084c42eb0bb06145ad50a45077e650d0

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

@@ -85,7 +85,8 @@ public class StorageWizardMigrateConfirm extends StorageWizardBase {
 
             if (Objects.equals(mVolume.getFsUuid(), sm.getPrimaryStorageVolume().getUuid())) {
                 final Intent intent = new Intent(this, StorageWizardReady.class);
-                intent.putExtra(DiskInfo.EXTRA_DISK_ID, mDisk.getId());
+                intent.putExtra(DiskInfo.EXTRA_DISK_ID,
+                        getIntent().getStringExtra(DiskInfo.EXTRA_DISK_ID));
                 startActivity(intent);
                 finishAffinity();