fix: fail to get empty index num rows

[smellthemoon]

#39125

[mergify]

@smellthemoon go-sdk check failed, comment rerun go-sdk can trigger the job again.

[smellthemoon]

rerun go-sdk

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 81.14%. Comparing base (826b726) to head (9a8a734).
Report is 11 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/core/src/index/ScalarIndexSort.cpp	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #39155      +/-   ##
==========================================
- Coverage   81.16%   81.14%   -0.02%     
==========================================
  Files        1395     1395              
  Lines      197277   197279       +2     
==========================================
- Hits       160124   160089      -35     
- Misses      31539    31575      +36     
- Partials     5614     5615       +1     

Components	Coverage Δ
Client	79.53% <ø> (ø)
Core	69.64% <75.00%> (-0.01%)	⬇️
Go	83.08% <ø> (-0.02%)	⬇️

Files with missing lines	Coverage Δ
internal/core/src/index/ScalarIndexSort.cpp	70.00% <75.00%> (-0.20%)	⬇️

... and 26 files with indirect coverage changes

[czs007]

/approve
/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: czs007, smellthemoon

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• internal/core/OWNERS [czs007]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment