Card component doesn't display loading block when it doesn't have children

[ReedSun]

Version

3.2.0

Environment

OS: Window 10, Brower: Google Chrome 63.0.3239.132,

Reproduction link

https://codesandbox.io/s/vynlqq63wl

Steps to reproduce

Use Card Component, set prop loading=true and don't set children.

What is expected?

Display loading block.

What is actually happening?

The loading block is not displayed.

---

ant-design/components/card/index.tsx

Line 195 in ca6a8d1

{children ? body : null}

I think maybe this line of code leads to this phenomenon.

I don't kown this phenomenon is a bug or is a feature, so I create this issue. If it's not a bug, it will be fine to close this issue.

^_^