Merge remote-tracking branch 'origin/master'

mec-biz/src/main/java/com/ym/mec/biz/service/impl/ClassGroupServiceImpl.java

@@ -634,6 +634,9 @@ public class ClassGroupServiceImpl extends BaseServiceImpl<Integer, ClassGroup>
             musicGroup.setSettlementType(type);
             musicGroupDao.update(musicGroup);
         }
+        if(classGroupAndTeachers == null || classGroupAndTeachers.size()==0){
+            return null;
+        }
 
         List<Integer> classGroupIds = classGroupAndTeachers.stream().map(ClassGroupTeachersDto::getId).collect(Collectors.toList());