okButtonDidTap method Null safety

Implementation

okButtonDidTap(BuildContext context) async {
  if (_isSubmitting) return;
  _isSubmitting = true;

  final String farmId = farmCodeController.text.trim();
  final bool result = await ApiService().userJoinFarm(farmId);

  if (farmId.isEmpty) {
    EventService().eventBus.fire(PopupEvent(
        type: PopupType.alert,
        action: PopupAction.show,
        data: {"title": "농장코드 입력", "content": "올바른 농장코드를 입력하세요."},
        onClose: () {
          Navigator.of(context, rootNavigator: true).popUntil((route) => !route.settings.name!.startsWith(PopupScreen.routeName));
        }));
  }

  if (result) {
    EventService().eventBus.fire(PopupEvent(
        type: PopupType.alert,
        action: PopupAction.show,
        data: {"title": "농장등록성공", "content": "농장이 정상적으로 등록되었습니다."},
        onClose: () {
          Navigator.of(context, rootNavigator: true).popUntil((route) => !route.settings.name!.startsWith(PopupScreen.routeName));
          Navigator.of(context, rootNavigator: true).pushReplacementNamed(FarmLoadingScreen.routeName);
        }));
  } else {
    EventService().eventBus.fire(PopupEvent(
        type: PopupType.alert,
        action: PopupAction.show,
        data: {"title": "농장등록 실패", "content": "농장등록에 실패했습니다."},
        onClose: () {
          Navigator.of(context, rootNavigator: true).popUntil((route) => !route.settings.name!.startsWith(PopupScreen.routeName));
        }));
  }
  _isSubmitting = false;
}