fix(schematics): ng add failed when call twice

[Nicoss54]

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?

If you run the schematics twice, one time after another one the second time the schematics fails with getText of undefined.

Issue Number: N/A

What is the new behavior?

It not failed anymore

Does this PR introduce a breaking change?

• Yes
• No

Other information

[zorro-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.06%. Comparing base (f4b9ba8) to head (2121f32).
Report is 50 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9171      +/-   ##
==========================================
- Coverage   92.10%   92.06%   -0.04%     
==========================================
  Files         561      561              
  Lines       20009    20009              
  Branches     3009     3009              
==========================================
- Hits        18430    18422       -8     
- Misses       1239     1247       +8     
  Partials      340      340              

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[Laffery]

I find an issue #8967 which might be related, I will take a review later

[Nicoss54]

@Laffery oh yes, I saw this issue et that why I made this fix. Apologies for forgotten to link the issue :/

[Laffery]

LGTM