考生编辑时，不能修改证件号

src/features/examwork/ExamStudentManagement/ExamStudentManagementDialog.vue

@@ -48,7 +48,7 @@
       </el-row>
       <el-row>
         <el-form-item label="证件号">
-          <el-input v-model.trim="form.identity"></el-input>
+          <el-input :disabled="isEdit" v-model.trim="form.identity"></el-input>
         </el-form-item>
       </el-row>
       <el-row>
@@ -89,7 +89,7 @@ export default {
   },
   computed: {
     isEdit() {
-      return this.examStudent.id;
+      return !!this.examStudent.id;
     },
   },
   data() {