fix: Stop splitfields iterator at eol in simd branch

[ritchie46]

fixes #23651

[github-actions]

The uncompressed lib size after this PR is 42.1272 MB.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.30%. Comparing base (901f5f2) to head (b9851fe).
Report is 14 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #23652      +/-   ##
==========================================
- Coverage   81.41%   81.30%   -0.11%     
==========================================
  Files        1640     1642       +2     
  Lines      222747   223187     +440     
  Branches     2837     2837              
==========================================
+ Hits       181342   181461     +119     
- Misses      40706    41027     +321     
  Partials      699      699              

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