fix(module: code-editor): fix wrong initialization with diff mode

[simplejason]

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?

wrong initialization with diff mode

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[zorro-bot]

This preview will be available after the checks is complete.

[wzhudev]

LGTM

[codecov]

Codecov Report

Merging #4485 into 8.x will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##              8.x    #4485      +/-   ##
==========================================
- Coverage   92.23%   92.22%   -0.01%     
==========================================
  Files         522      522              
  Lines       11107    11108       +1     
  Branches     2018     2018              
==========================================
  Hits        10244    10244              
- Misses        436      437       +1     
  Partials      427      427

Impacted Files	Coverage Δ
components/code-editor/nz-code-editor.component.ts	10.52% <0%> (-0.15%)	⬇️

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