this.data可能为undefined,需要判断一下

* form-item sizeClass

* Update form.spec.js

Added forgotten translation for page

* Table: support manually sorting. Resolves #9495

* Table: add parameters for sort api

* Docs: improve docs

* Docs: fix docs of Tab-pane

* Radio: support switching radio with keyborard in ff. Fixes #8198

* add support of tab penl lazy render

* add docs

* fix test

* Tabs: update tab-pane.d.ts

* Docs: update Tabs docs

* Upload: fix beforeUpload hook bug

* Upload: add ElUploadInternalRawFile interface

让circle button也支持size属性控制，padding的大小根据size属性的```button-padding-vertical```确定

* Tabs: add before-leave hook

* Tabs: update tabs.d.ts