getBody method Null safety

Implementation

@override
List<Widget> getBody() {
  final List<Widget> result = <Widget>[];
  if (group.warning != null) {
    result.add(
      Container(
        color: SmoothTheme.getColor(
          Theme.of(context).colorScheme,
          WARNING_COLOR,
          ColorDestination.BUTTON_BACKGROUND,
        ),
        width: double.infinity,
        padding: const EdgeInsets.all(LARGE_SPACE),
        margin: const EdgeInsets.all(LARGE_SPACE),
        child: Text(
          group.warning ?? appLocalizations.unknown,
          style: TextStyle(
            color: SmoothTheme.getColor(
              Theme.of(context).colorScheme,
              WARNING_COLOR,
              ColorDestination.BUTTON_FOREGROUND,
            ),
          ),
        ),
      ),
    );
  }
  final List<String> excludedAttributeIds =
      userPreferences.getExcludedAttributeIds();
  for (final Attribute attribute in group.attributes!) {
    if (excludedAttributeIds.contains(attribute.id)) {
      continue;
    }
    result.add(AttributeButton(attribute, productPreferences));
  }
  return result;
}