fix(module:sf:checkbox): fix invalid indeterminate status

[cipchk]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ng-alain/delon/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
[x] No

Other information

[codecov-io]

Codecov Report

Merging #433 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #433      +/-   ##
==========================================
+ Coverage   99.09%   99.09%   +<.01%     
==========================================
  Files         257      257              
  Lines        6730     6742      +12     
  Branches      678      681       +3     
==========================================
+ Hits         6669     6681      +12     
  Misses         31       31              
  Partials       30       30

Impacted Files	Coverage Δ
packages/form/src/model/form.property.ts	95.54% <ø> (ø)	⬆️
...kages/form/src/widgets/checkbox/checkbox.widget.ts	98% <100%> (ø)	⬆️
packages/form/src/validator.factory.ts	100% <100%> (ø)	⬆️
packages/abc/edit/edit.component.ts	100% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2505971...c944570. Read the comment docs.