enhance: Remove an undefined behavior in index writer

[sunby]

No description provided.

[mergify]

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

[sunby]

/run-cpu-e2e

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.02%. Comparing base (90de37e) to head (1b40e0e).
Report is 55 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #38657      +/-   ##
==========================================
- Coverage   81.05%   81.02%   -0.03%     
==========================================
  Files        1381     1380       -1     
  Lines      195090   195145      +55     
==========================================
- Hits       158131   158124       -7     
- Misses      31398    31441      +43     
- Partials     5561     5580      +19     

Components	Coverage Δ
Client	78.26% <ø> (ø)
Core	69.33% <ø> (ø)
Go	83.01% <ø> (-0.04%)	⬇️

see 45 files with indirect coverage changes

[aoiasd]

/lgtm

[tedxu]

/approve

[sre-ci-robot]

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