fix: 脑图顺序添加多个用例时顺序错乱

--bug=1011900 --user=陈建星 [测试跟踪]github#12269脑图，列表切换后，脑图用例顺序全乱 https://www.tapd.cn/55049933/s/1160637

backend/src/main/java/io/metersphere/track/service/TestCaseService.java

@@ -1926,6 +1926,8 @@ public class TestCaseService {
 
             String lastAddId = null;
 
+            String lastAddId = null;
+
             for (TestCaseMinderEditRequest.TestCaseMinderEditItem item : data) {
                 if (StringUtils.isBlank(item.getNodeId()) || item.getNodeId().equals("root")) {
                     item.setNodeId("");