Fix vectorAngle when nan exists

[swhitty]

Fixes issue where some Arc segments calculate NaN which result in trap when converting to Int.

func vectorAngle() would previously return NaN if any of its arguments were NaN, this change clamps NaN to 1.0 avoiding a crash.

The drawn path segment may still be incorrect, but the program should no longer crash.

reported in: #64

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.02%. Comparing base (3f470d7) to head (f36e1d4).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #65   +/-   ##
=======================================
  Coverage   85.02%   85.02%           
=======================================
  Files          78       78           
  Lines        7191     7191           
=======================================
  Hits         6114     6114           
  Misses       1077     1077           

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