fix(select): emit array when resetting multiple select

[yggg]

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• I read and followed the CONTRIBUTING.md guide.
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Short description of what this resolves:

Reset emitted null as a select value for multiple select which caused Can't assign a single value if select is marked as multiple error when trying to set null value back (two-way data binding).

[codecov]

Codecov Report

Merging #1399 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1399   +/-   ##
=======================================
  Coverage   81.84%   81.84%           
=======================================
  Files         232      232           
  Lines        7067     7067           
  Branches      600      601    +1     
=======================================
  Hits         5784     5784           
  Misses       1104     1104           
  Partials      179      179

Impacted Files	Coverage Δ
...mework/theme/components/select/select.component.ts	90.16% <100%> (ø)	⬆️