When clearing the search query of select options with nzCustomContent enabled some options are empty.

[CipherdevNL]

Reproduction link

https://stackblitz.com/edit/ng-zorro-antd-start-z6h7vm

Steps to reproduce

• Go to https://ng.ant.design/components/select/en#components-select-demo-custom-content
• Go to the section about custom option template
• Fill Mac as search query
• Clear the search query

What is expected?

It should show the Windows option with its custom content

What is actually happening?

The option is not showing the original content before search.

Environment	Info
ng-zorro-antd	9.1.0
Browser	Firefox 75.0 64Bits on MacOS

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I ran into this bug when creating an phone number component. After searching for the calling code it will have a list with empty content. Only after scrolling they will reappear.

The stackblitz has the same code used inside the demo. But in the stackblitz it works :/

[zmzimpl]

same issue here!

[bilalucar]

Because of this problem, we did not upgrade our project to Angular 9. Hopefully it will be fixed as soon as possible.

[vthinkxie]

Hi all, the bug is caused by the virtual scroll of @angular/cdk
the diff strategy and template cache has something wrong in this situation
ref angular/components#15838
set cdkVirtualForTemplateCacheSize to 0 as a temp solution