fix(module:select): fix space closing select panel

[wzhudev]

close #2201

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: #2201

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #2240 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #2240   +/-   ##
=======================================
  Coverage   95.96%   95.96%           
=======================================
  Files         482      482           
  Lines       11965    11965           
  Branches     1594     1594           
=======================================
  Hits        11482    11482           
  Misses        134      134           
  Partials      349      349

Impacted Files	Coverage Δ
components/select/nz-select.component.ts	96.75% <100%> (ø)	⬆️

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