refactor: Improve error message for Zero-Field Structs with Parquet

[coastalwhite]

Related to #19352.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 80.21%. Comparing base (8a76dad) to head (0358685).
Report is 70 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-parquet/src/arrow/write/schema.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19370      +/-   ##
==========================================
- Coverage   80.24%   80.21%   -0.03%     
==========================================
  Files        1523     1523              
  Lines      209545   209859     +314     
  Branches     2434     2434              
==========================================
+ Hits       168148   168345     +197     
- Misses      40842    40959     +117     
  Partials      555      555              

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