fix(contrib/polaris): incorrect conversion between integer types

[demoManito]

Description (what this PR does / why we need it):

https://github.com/go-kratos/kratos/security/code-scanning/3

Which issue(s) this PR fixes (resolves / be part of):

Other special notes for the reviewers:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.96%. Comparing base (f715eb0) to head (8d2db86).
Report is 7 commits behind head on main.

❗ Current head 8d2db86 differs from pull request most recent head 18d5f54. Consider uploading reports for the commit 18d5f54 to get more accurate results

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3300      +/-   ##
==========================================
+ Coverage   81.93%   81.96%   +0.03%     
==========================================
  Files          92       92              
  Lines        4206     4203       -3     
==========================================
- Hits         3446     3445       -1     
+ Misses        580      579       -1     
+ Partials      180      179       -1     

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