hotfix: 修复了个奇怪的地方

dao/checkin.go

@@ -87,7 +87,7 @@ func (c CheckinDAO) FindAllActivities(isTeacher bool) []po.Activity {
 	var err error
 	// 按照主键排序
 	if isTeacher {
-		err = c.Tx.Find(&arr, "teacher_available=? and visible=", true, true).Order("id").Error
+		err = c.Tx.Find(&arr, "visible=?", true).Order("id").Error
 	} else {
 		err = c.Tx.Find(&arr, "visible=?", true).Order("id").Error
 	}