fix: Clear NaNs due to zero-weight division in rolling var/std

[orlp]

Fixes #21758.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.13%. Comparing base (d671d3c) to head (c42eb34).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21761      +/-   ##
==========================================
+ Coverage   81.06%   81.13%   +0.06%     
==========================================
  Files        1610     1612       +2     
  Lines      233050   233373     +323     
  Branches     2689     2687       -2     
==========================================
+ Hits       188927   189340     +413     
+ Misses      43492    43403      -89     
+ Partials      631      630       -1     

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