fix: 脑图编辑用例会清除标签

--bug=1013352 --user=陈建星 【测试跟踪】github# 13783 脑图新增用例操作步骤后，已经保存的标签会被清除 https://www.tapd.cn/55049933/s/1164680

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

@@ -1965,6 +1965,7 @@ public class TestCaseService {
                     EditTestCaseRequest editRequest = new EditTestCaseRequest();
                     BeanUtils.copyBean(editRequest, item);
                     editRequest.setCustomFields(null);
+                    editRequest.setTags(null);
                     editTestCase(editRequest);
                     changeOrder(item, request.getProjectId());
                     lastAddId = null;