removeGroupRule method
Remove group rule.
Implementation
void removeGroupRule(int index) {
final current = selected;
if (current == null) return;
draft ??= NmZoneDraft(current);
final rules = List<NmGroupRule>.of(draft!.working.groupRules);
if (index < 0 || index >= rules.length) return;
rules.removeAt(index);
draft!.working = draft!.working.copyWith(groupRules: rules);
notifyListeners();
}