fix(sheet): maybe get null when get active sheet

[Dushusir]

Pull Request Checklist

• Related tickets or issues have been linked in the PR description (or missing issue).
• Naming convention is followed (do please check it especially when you created new plugins, commands and resources).
• Unit tests have been added for the changes (if applicable).
• Breaking changes have been documented (or no breaking changes introduced in this PR).

[wzhudev]

LGTM

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 14.45783% with 213 lines in your changes missing coverage. Please review.

Project coverage is 27.16%. Comparing base (b6ef910) to head (d3d847c).

Files	Patch %	Lines
...e/src/controllers/sheet-find-replace.controller.ts	0.00%	15 Missing ⚠️
...ckages/sheets-ui/src/controllers/menu/menu-util.ts	7.14%	13 Missing ⚠️
...atting-ui/src/components/panel/rule-list/index.tsx	0.00%	9 Missing ⚠️
.../render-controllers/selection.render-controller.ts	0.00%	9 Missing ⚠️
...lers/render-controllers/sheet-render.controller.ts	0.00%	7 Missing ⚠️
...s-data-validation/src/controllers/dv.controller.ts	0.00%	6 Missing ⚠️
packages/facade/src/apis/sheets/f-workbook.ts	37.50%	5 Missing ⚠️
...atting-ui/src/components/panel/rule-edit/index.tsx	0.00%	5 Missing ⚠️
...-conditional-formatting-ui/src/menu/manage-rule.ts	0.00%	5 Missing ⚠️
...ers/render-controllers/freeze.render-controller.ts	0.00%	5 Missing ⚠️
... and 62 more

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #2512      +/-   ##
==========================================
- Coverage   27.17%   27.16%   -0.02%     
==========================================
  Files        1654     1654              
  Lines       83352    83476     +124     
  Branches    17266    17356      +90     
==========================================
+ Hits        22654    22673      +19     
- Misses      60698    60803     +105     

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