[BUG] fix default data source bug

[BionIT]

Description

In https://github.com/opensearch-project/OpenSearch-Dashboards/pull/6237/files, we introduced default data source, and expect that if default data source is not set, the get call to uisettings would return null, which is not always the case. See in the recordings that for cases that a default data source is accidentally removed from UI, the data source id is empty string from api/opensearch-dashboards/settings API call. Thus instead of checking if the returned value is exactly null, we need to check if it is not blank/empty.

Issues Resolved

fixes #6835

Screenshot

fixdefault.mp4

Testing the changes

In the recording, the following steps were performed:

• enable data source

before change:

• check the api/opensearch-dashboards/settings which has empty string for the default data source
• creating data source will not make it default data source

after change:

• check the api/opensearch-dashboards/settings which has empty string for the default data source
• creating data source will make it default data source

Changelog

• fix: fix not setting the default data source when creating data source bug

Check List

• All tests pass
  • yarn test:jest
  • yarn test:jest_integration
• New functionality includes testing.
• New functionality has been documented.
• Update CHANGELOG.md
• Commits are signed per the DCO using --signoff

[zhongnansu]

lgtm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.40%. Comparing base (016dcfd) to head (14b4e42).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6908   +/-   ##
=======================================
  Coverage   67.39%   67.40%           
=======================================
  Files        3444     3444           
  Lines       67847    67847           
  Branches    11035    11035           
=======================================
+ Hits        45727    45733    +6     
+ Misses      19452    19448    -4     
+ Partials     2668     2666    -2     

Flag	Coverage Δ
Linux_1	33.08% <ø> (ø)
Linux_2	55.12% <ø> (ø)
Linux_3	45.25% <100.00%> (ø)
Linux_4	34.82% <0.00%> (ø)
Windows_1	?
Windows_2	55.09% <ø> (ø)
Windows_3	45.26% <100.00%> (?)
Windows_4	34.82% <0.00%> (ø)

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[zhyuanqi]

Hi Lu. Thanks for fixing the issue. For cases that a default data source is accidentally removed from UI, you mean that customer delete the datasource?