同步练习bug修复

src/components/MxCondition/condition-object/condition-exe-grade.js

@@ -13,7 +13,7 @@ export default {
   title: '学册',
   getList: function(param,$ref) {
     return new Promise((resolve, reject) => {
-      smartGradeList({subjectId:$ref.model.exeSubject,editionId:param.exeOrder}).then(res => resolve(res.data))
+      smartGradeList({subjectId:$ref.model.exeSubject,editionId:param.exeOrder}).then(res => resolve(res.data  || []))
         .catch(e => reject(e))
     })
   },