fix：网络教师签到

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

@@ -144,6 +144,7 @@ public class CourseScheduleTeacherSalaryServiceImpl extends BaseServiceImpl<Long
                         courseScheduleTeacherSalary.setExpectSalary(offlineTeacherSalary);
                     }
                 }
+                courseScheduleTeacherSalary.setActualSalary(null);
                 if (Objects.isNull(courseScheduleTeacherSalary.getId())) {
                     courseScheduleTeacherSalaries.add(courseScheduleTeacherSalary);
                 } else {