update 树形结构

src/main/java/cn/teammodel/controller/admin/service/impl/AdminIndexDutyServiceImpl.java

@@ -234,7 +234,7 @@ public class AdminIndexDutyServiceImpl implements AdminIndexDutyService {
             lessonRecordDto.setSubjectId(subjectIds);
 
             if(subjectIds.isEmpty()) {
-                return null;
+                return new HashMap<>();
             }
         }
         mapper =  GroupUtil.getGroupId(lessonRecordDto,new GroupUtil(env), request,url);

src/main/java/cn/teammodel/model/entity/appraise/AppraiseTreeNode.java

@@ -4,6 +4,7 @@ import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import lombok.Data;
 
+import java.util.ArrayList;
 import java.util.List;
 
 @Data
@@ -31,5 +32,5 @@ public class AppraiseTreeNode {
     @JsonProperty("isPraise")
     boolean isPraise;
 
-    List<AppraiseTreeNode> children;
+    List<AppraiseTreeNode> children = new ArrayList<>();
 }