fix(module:select): shaking when closing dropdown if use a TemplateRef as notFoundContent (#8931)

[keke521jie]

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?

• 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: close #8931

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.13%. Comparing base (b0a4287) to head (f3b7740).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #9336    +/-   ##
========================================
  Coverage   92.12%   92.13%            
========================================
  Files         561      561            
  Lines       19631    19630     -1     
  Branches     3107     3000   -107     
========================================
+ Hits        18086    18087     +1     
  Misses       1206     1206            
+ Partials      339      337     -2     

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[Laffery]

LGTM