fix: Infinite recursion when broadcasting into struct zip_outer_validity

[coastalwhite]

Fixes #21267.

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 79.87%. Comparing base (4ef23d8) to head (e2852c7).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...es/polars-core/src/chunked_array/comparison/mod.rs	90.90%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #21268   +/-   ##
=======================================
  Coverage   79.87%   79.87%           
=======================================
  Files        1596     1596           
  Lines      228470   228489   +19     
  Branches     2607     2607           
=======================================
+ Hits       182488   182515   +27     
+ Misses      45386    45378    -8     
  Partials      596      596           

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