PageInfo: fix zero-division check

[agoujot]

A division by zero happened today at https://xtools.wmcloud.org/pageinfo/pl.wikipedia.org/Mi%C4%99dzynarodowy%20Bank%20Inwestycyjny/2025-07-12/2025-07-12. it's a weird request to make (pageinfo for exactly two edits including one revdeleted and the rollback), but whatever. We were ensuring that the wrong thing was non-0.

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 60.69%. Comparing base (4b8eb28) to head (3752045).
⚠️ Report is 232 commits behind head on main.

Files with missing lines	Patch %	Lines
src/Model/PageInfo.php	75.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##               main     #609       +/-   ##
=============================================
- Coverage     71.30%   60.69%   -10.62%     
- Complexity     1275     1409      +134     
=============================================
  Files            46       46               
  Lines          3792     4320      +528     
=============================================
- Hits           2704     2622       -82     
- Misses         1088     1698      +610     

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