fix(SelectControl): select zero value

[rekilina]

SUMMARY

If SelectControl has options with numeric values, then the value 0 can be selected.
In this case, if defaultValue is not set or it is set to undefined, then currentValue will be set to undefined instead of 0.
This fix allows correctly save SelectControl with selected option, which value equals to 0, when the default value is undefined.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

1. Create SelectControl instance in the controlPanel and set choices with numeric value:
   [[0, "label_1"], [1, "label_2"]]
   Don't specify default value or set default value to undefined.
2. Select option with value 0 and save chart.
3. Reload page and check, whether the SelectControl has selected value.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b6d433d) 69.17% compared to head (8e5fc3c) 69.17%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #26353   +/-   ##
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  Coverage   69.17%   69.17%           
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  Files        1945     1945           
  Lines       75979    75979           
  Branches     8476     8476           
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  Hits        52562    52562           
  Misses      21227    21227           
  Partials     2190     2190           

Flag	Coverage Δ
javascript	56.52% <100.00%> (ø)

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[villebro]

Great catch! I would have asked if you could add a test, but I see this is one of those old non-TS pieces of code that likely doesn't have good tests to begin with. So LGTM.

[villebro]

@rekilina I didn't have my laptop handy yesterday, but I noticed now that there's SelectControl.test.jsx where you should be able to add a test for this. Would you be able to take a stab at that?

[villebro]

@rekilina I'll go ahead and merge this one and follow up with a test PR, as the test suite is arguably pretty messy in its current state. But if you want to add the test, let me know by tagging me here so I can avoid opening a new PR for it.