[bug report] the first page is blank by default when the El image label is opened

[syp2850]

Element UI version

0.1.0

OS/Browsers version

mac/chrome

Vue version

3.0.0-alpha.10

Reproduction Link

https://codepen.io/pen/?&editable=true

Steps to reproduce

点击图片 默认第一个是空白

What is Expected?

默认第一张

What is actually happening?

默认第一个是空白，如果只传递一张图片，会因为跳转摁钮消失 而无法显示图片

[element-bot]

Translation of this issue:

Element UI version

0.1.0

OS/Browsers version

Mac/chrome

Vue version

3.0.0-alpha.10

Reproduction Link

https://codepen.io/pen/?&editable=true

Steps to reproduce

Click the picture. The first one is blank by default

What is Expected?

Default first sheet

What is actually happening?

The first one is blank by default. If only one picture is passed, the picture will not be displayed because the jump button disappears

[scscms]

这个组件必须吐槽，

data() {
      return {
        url: 'a.jpeg',
        srcList: [
          'a.jpeg', //注意这里！
          'b.jpeg'
        ]
      }
    }

只有当srcList第一个元素等于url时才不会空白，这完全是违背缩略图规则！
同时建议添加一个属性配置，可以选择再次点击预览图片时是否应该强制返回第一张图片！

[haoyaxin]

官网例子可以复现这个bug

[luckyCao]

#18975