修正组合测量项完成后未保留

lib/process/workspace/application.dart

@@ -418,7 +418,7 @@ class Application implements IApplication {
   void _handleBeforeSwitchItem() {
     if (activeMeasureItem == null) return;
     final item = activeMeasureItem!;
-    if (item is TopMeasureItem) {
+    if (item is TopMeasureItem && item.feature != null) {
       bool isAllEmpty =
           item.childItems.every((e) => e.measuredFeatures.isEmpty);
       if (isAllEmpty) {