fix(select): allow initial falsy values

[yggg]

Please read and mark the following check list before creating a pull request:

• I read and followed the CONTRIBUTING.md guide.
• I read and followed the New Feature Checklist guide.

Short description of what this resolves:

[codecov]

Codecov Report

Merging #1936 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1936   +/-   ##
=======================================
  Coverage   84.08%   84.08%           
=======================================
  Files         234      234           
  Lines        7723     7723           
  Branches      679      679           
=======================================
  Hits         6494     6494           
  Misses       1031     1031           
  Partials      198      198

Impacted Files	Coverage Δ
...mework/theme/components/select/select.component.ts	89.96% <100%> (ø)	⬆️