fix(module:nz-tree-select): fix error when judging multiple instance condition

[EnochGao]

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?

An error is reported when judging multiple instance conditions
https://stackblitz.com/edit/kzn1gfa7-2qtub7c7?file=src%2Fapp%2Fapp.component.ts

Issue Number: #8983

What is the new behavior?

Multiinstance normal

Does this PR introduce a breaking change?

• Yes
• [ x] No

Other information

[zorro-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.94%. Comparing base (1f8f4da) to head (40866bb).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9008   +/-   ##
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  Coverage   91.94%   91.94%           
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  Files         555      555           
  Lines       19708    19708           
  Branches     2946     2945    -1     
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  Hits        18121    18121           
  Misses       1261     1261           
  Partials      326      326           

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