Fix up Network and Internet Slice

- Fix pref key for Airplane mode
- Return null when no mobile data is available

Test: robotests
Fixes: 130244854
Change-Id: I88806cb9215af159114ac150c20cdb8fb413befe

src/com/android/settings/network/telephony/MobileDataSlice.java

@@ -46,6 +46,7 @@ import com.android.settings.slices.SliceBackgroundWorker;
 import com.google.common.annotations.VisibleForTesting;
 
 import java.io.IOException;
+import java.util.List;
 
 /**
  * Custom {@link Slice} for Mobile Data.
@@ -71,6 +72,11 @@ public class MobileDataSlice implements CustomSliceable {
 
     @Override
     public Slice getSlice() {
+        // Mobile data not available, thus return no Slice.
+        if (!isMobileDataAvailable()) {
+            return null;
+        }
+
         final IconCompat icon = IconCompat.createWithResource(mContext,
                 R.drawable.ic_network_cell);
         final String title = mContext.getText(R.string.mobile_data_settings_title).toString();
@@ -178,6 +184,16 @@ public class MobileDataSlice implements CustomSliceable {
                 intent, 0 /* flags */);
     }
 
+    /**
+     * @return {@code true} when mobile data is not supported by the current device.
+     */
+    private boolean isMobileDataAvailable() {
+        final List<SubscriptionInfo> subInfoList =
+                mSubscriptionManager.getSelectableSubscriptionInfoList();
+
+        return !(subInfoList == null || subInfoList.isEmpty());
+    }
+
     @VisibleForTesting
     boolean isAirplaneModeEnabled() {
         // Generic key since we only want the method check - no UI.