fix(form:select): fix invlaid tag count

[cipchk]

• close sf组件中，select 多选模式，选项不能正常显示 ng-alain#1089

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

@@          Coverage Diff           @@
##           master    #571   +/-   ##
======================================
  Coverage    98.7%   98.7%           
======================================
  Files         260     260           
  Lines        7424    7424           
  Branches     1105    1105           
======================================
  Hits         7328    7328           
  Misses         33      33           
  Partials       63      63

Impacted Files	Coverage Δ
packages/form/src/widgets/select/select.widget.ts	83.78% <100%> (ø)	⬆️

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