fix(module:tooltip): fix not undefined value not updated

[wzhudev]

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

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

[codecov]

Codecov Report

Merging #4392 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #4392   +/-   ##
======================================
  Coverage    92.2%   92.2%           
======================================
  Files         520     520           
  Lines       11039   11039           
  Branches     1997    1997           
======================================
  Hits        10178   10178           
  Misses        429     429           
  Partials      432     432

Impacted Files	Coverage Δ
...mponents/tooltip/base/nz-tooltip-base.directive.ts	91.08% <100%> (ø)	⬆️

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[vthinkxie]

LGTM