fix: process null value in yaml

[foxspy]

issue: #34298
fix key: null defined in the yaml file.
viper will parse it as "", and yaml v3 will parse it as "null".

[mergify]

@foxspy cpp-unit-test check failed, comment rerun cpp-unit-test can trigger the job again.

[foxspy]

rerun cpp-unit-test

[mergify]

@foxspy E2e jenkins job failed, comment /run-cpu-e2e can trigger the job again.

[yanliang567]

let's unblock deployment issue first, manual pass for a known e2e test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.00%. Comparing base (c27f477) to head (73ae9bb).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #37418      +/-   ##
==========================================
- Coverage   83.24%   81.00%   -2.24%     
==========================================
  Files        1015     1305     +290     
  Lines      157453   182885   +25432     
==========================================
+ Hits       131064   148150   +17086     
- Misses      21192    29542    +8350     
+ Partials     5197     5193       -4     

Components	Coverage Δ
Client	∅ <ø> (∅)
Core	67.17% <66.66%> (∅)
Go	83.26% <100.00%> (-0.01%)	⬇️

Files with missing lines	Coverage Δ
pkg/config/config.go	80.00% <100.00%> (+1.73%)	⬆️

... and 316 files with indirect coverage changes

[congqixia]

/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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