doing #19407 完善费用报销单

lib/features/expense/widgets/expense_detail_dialog.dart

@@ -934,7 +934,9 @@ class _ExpenseDetailDialogState extends State<ExpenseDetailDialog> {
   Widget _buildAcctSubjectCard(AppColorsExtension colors) {
     return _readOnlyCard(
       label: _l10n.get('acctSubject'),
-      value: '${_selCat.acctSubjectId}/${_selCat.acctSubjectName}',
+      value: _selCat.acctSubjectId.isNotEmpty
+          ? '${_selCat.acctSubjectId}/${_selCat.acctSubjectName}'
+          : '',
       colors: colors,
     );
   }