Fix battery tip app name is empty

- Top waste app is linux process not android process. Therefore
it doesn't contains application label. Fixed by return the process
name if packages label is empty.

Fixes: 146558570
Test: follow the steps:
1. adb shell settings put global battery_tip_constants test_low_battery_tip=true
2. Unplug usb. Go to Settings -> Battery, it should show an item
"Phone used more than usual"
3. Click "phone used more than usual" item, all the items should
have title and icon.

Change-Id: I85c232bc6a048b3104c4fce0fcec2b944e8ac1b4

src/com/android/settings/fuelgauge/batterytip/HighUsageAdapter.java

@@ -30,7 +30,6 @@ import androidx.recyclerview.widget.RecyclerView;
 
 import com.android.settings.R;
 import com.android.settings.Utils;
-import com.android.settingslib.utils.StringUtil;
 
 import java.util.List;
 
@@ -78,7 +77,12 @@ public class HighUsageAdapter extends RecyclerView.Adapter<HighUsageAdapter.View
         holder.appIcon.setImageDrawable(
                 Utils.getBadgedIcon(mIconDrawableFactory, mPackageManager, app.packageName,
                         UserHandle.getUserId(app.uid)));
-        holder.appName.setText(Utils.getApplicationLabel(mContext, app.packageName));
+        CharSequence label = Utils.getApplicationLabel(mContext, app.packageName);
+        if (label == null) {
+            label = app.packageName;
+        }
+
+        holder.appName.setText(label);
     }
 
     @Override