fix(module:cascader): restore its value after cancel search

[stygian-desolator]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

close #6036

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #6088 (6696490) into master (3204927) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #6088   +/-   ##
=======================================
  Coverage   89.89%   89.89%           
=======================================
  Files         465      465           
  Lines       14057    14097   +40     
  Branches     2311     2237   -74     
=======================================
+ Hits        12636    12673   +37     
+ Misses        873      872    -1     
- Partials      548      552    +4     

Impacted Files	Coverage Δ
components/cascader/cascader.component.ts	94.51% <100.00%> (-0.16%)	⬇️
components/tree-select/tree-select.component.ts	90.13% <0.00%> (-3.43%)	⬇️
components/table/src/table-style.service.ts	94.82% <0.00%> (-1.73%)	⬇️
components/core/config/config.ts	100.00% <0.00%> (ø)
components/cascader/cascader-li.component.ts	100.00% <0.00%> (ø)
components/drawer/drawer.component.ts	97.88% <0.00%> (+0.03%)	⬆️
components/pagination/pagination.component.ts	98.63% <0.00%> (+0.12%)	⬆️
components/time-picker/time-holder.ts	95.78% <0.00%> (+1.05%)	⬆️
components/core/util/text-measure.ts	91.30% <0.00%> (+1.73%)	⬆️
... and 2 more

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[wzhudev]

LGTM. Just a codestyle change requested.

[wzhudev]

Use else.