虚拟滚动中， 数据量少时，表头不对齐

[liwei511]

Reproduction link

https://stackblitz.com/edit/angular-qyhvs2?file=src/app/app.component.ts

Steps to reproduce

右侧表头不对齐

What is expected?

表头对齐

What is actually happening?

表头不对齐

Environment	Info
ng-zorro-antd	7.3.2
Browser	Chrome 74

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这个例子（官方文档里https://ng.ant.design/components/table/zh#components-table-demo-virtual）， 如果行数几行时， 表头不对齐。 期望大佬加一个overflow-y:scoll。

[ng-zorro-bot]

Translation of this issue:

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Virtual scrolling, when the amount of data is small, the header is not aligned

Reproduction link

[https://stackblitz.com/edit/angular-qyhvs2?file=src/app/app.component.ts](https://stackblitz.com/edit/angular-qyhvs2?file=src/app/app. Component.ts)

Steps to reproduce

The right header is not aligned

What is expected?

Head alignment

What is actually happening?

Header misalignment

Environment	Info
ng-zorro-antd	7.3.2
Browser	Chrome 74

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This example (https://ng.ant.design/components/table/zh#components-table-demo-virtual) in the official documentation, if the number of lines is a few lines, the headers are not aligned. Expect to add an overflow-y:scoll.