Update SliceView when slice is null

When it is null, we should also update SliceView, so SliceView can
update to be "invisible"

Fixes: 133790296
Test: RunSettingsRoboTests
Change-Id: I239405cce8bcadacbd374ccbb24d0fcbadc04880

src/com/android/settings/slices/SlicePreferenceController.java

@@ -40,7 +40,8 @@ public class SlicePreferenceController extends BasePreferenceController implemen
         LifecycleObserver, OnStart, OnStop, Observer<Slice> {
     @VisibleForTesting
     LiveData<Slice> mLiveData;
-    private SlicePreference mSlicePreference;
+    @VisibleForTesting
+    SlicePreference mSlicePreference;
     private Uri mUri;
 
     public SlicePreferenceController(Context context, String preferenceKey) {
@@ -82,8 +83,6 @@ public class SlicePreferenceController extends BasePreferenceController implemen
 
     @Override
     public void onChanged(Slice slice) {
-        if (slice != null) {
-            mSlicePreference.onSliceUpdated(slice);
-        }
+        mSlicePreference.onSliceUpdated(slice);
     }
 }

tests/robotests/src/com/android/settings/slices/SlicePreferenceControllerTest.java

@@ -41,6 +41,8 @@ public class SlicePreferenceControllerTest {
 
     @Mock
     private LiveData<Slice> mLiveData;
+    @Mock
+    private SlicePreference mSlicePreference;
     private Context mContext;
     private SlicePreferenceController mController;
     private Uri mUri;
@@ -53,6 +55,7 @@ public class SlicePreferenceControllerTest {
         mContext = spy(RuntimeEnvironment.application);
         mController = new SlicePreferenceController(mContext, KEY);
         mController.mLiveData = mLiveData;
+        mController.mSlicePreference = mSlicePreference;
         mUri = Uri.EMPTY;
     }
 
@@ -78,4 +81,11 @@ public class SlicePreferenceControllerTest {
         mController.onStop();
         verify(mLiveData).removeObserver(mController);
     }
+
+    @Test
+    public void onChanged_nullSlice_updateSlice() {
+        mController.onChanged(null);
+
+        verify(mController.mSlicePreference).onSliceUpdated(null);
+    }
 }