fix: Properly zip struct validities

[coastalwhite]

@kszlim

[codecov]

Codecov Report

Attention: Patch coverage is 79.47368% with 39 lines in your changes missing coverage. Please review.

Project coverage is 79.89%. Comparing base (58265f6) to head (f8b71c8).
Report is 62 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-core/src/chunked_array/ops/zip.rs	79.25%	39 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18886      +/-   ##
==========================================
- Coverage   79.94%   79.89%   -0.05%     
==========================================
  Files        1519     1520       +1     
  Lines      205869   206697     +828     
  Branches     2898     2906       +8     
==========================================
+ Hits       164572   165139     +567     
- Misses      40749    41010     +261     
  Partials      548      548              

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[kszlim]

Thanks @coastalwhite ! I've tested this and it fixes my issue!