[fix] update attribute which is list

ui/src/views/cmdb/ci/modules/EditableCell.vue

@@ -40,8 +40,10 @@ export default {
     joinList: function (itemValue) {
       if (typeof itemValue === 'object' && itemValue) {
         return itemValue.join(',')
+      } else if (itemValue !== null) {
+        return itemValue + ''
       } else {
-        return itemValue || ' '
+        return ''
       }
     }
   }