getBody method Null safety

Implementation

@override
List<Widget> getBody() {
  final List<AttributeGroup> groups =
      _reorderGroups(productPreferences.attributeGroups!);
  final List<Widget> result = <Widget>[
    ListTile(
      leading: const Icon(Icons.rotate_left),
      title: Text(appLocalizations.reset_food_prefs),
      onTap: () => _confirmReset(context),
    ),
  ];
  for (final AttributeGroup group in groups) {
    final AbstractUserPreferences abstractUserPreferences =
        UserPreferencesAttributeGroup(
      productPreferences: productPreferences,
      group: group,
      setState: setState,
      context: context,
      userPreferences: userPreferences,
      appLocalizations: appLocalizations,
      themeData: themeData,
    );

    result.addAll(abstractUserPreferences.getContent());
  }
  return result;
}