Approximate font metrics only when metrics don't exist

[ylemkimon]

Fix non-existent metrics error for \eth.

[codecov-io]

Codecov Report

Merging #1898 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1898      +/-   ##
==========================================
+ Coverage   94.76%   94.76%   +<.01%     
==========================================
  Files          79       79              
  Lines        4663     4664       +1     
  Branches      813      813              
==========================================
+ Hits         4419     4420       +1     
  Misses        220      220              
  Partials       24       24

Flag	Coverage Δ
#screenshotter	88.94% <100%> (ø)	⬆️
#test	86.79% <66.66%> (-0.02%)	⬇️

Impacted Files	Coverage Δ
src/fontMetrics.js	100% <100%> (ø)	⬆️

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[kevinbarabash]

Good call. Thanks for making this change.

[codecov-io]

Codecov Report

Merging #1898 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1898      +/-   ##
==========================================
+ Coverage   94.83%   94.83%   +<.01%     
==========================================
  Files          79       79              
  Lines        4783     4784       +1     
  Branches      845      845              
==========================================
+ Hits         4536     4537       +1     
  Misses        223      223              
  Partials       24       24

Flag	Coverage Δ
#screenshotter	89.33% <100%> (ø)	⬆️
#test	85.82% <66.66%> (-0.02%)	⬇️

Impacted Files	Coverage Δ
src/fontMetrics.js	100% <100%> (ø)	⬆️

---

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Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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