fix(Visibility): cancel RAF on component unmount

[layershifter]

Fixes #2570.
Replaces #2571.

Details

Visibility runs the update() method inside requestAnimationFrame(). It can be called after the component's unmount and will cause an exception as the ref inside the component stopped to exist.

This PR adds cancelAnimationFrame() to componentWillUnmount() that will stop RAF's action if component will be unmounted.

[codecov-io]

Codecov Report

Merging #2635 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2635      +/-   ##
==========================================
+ Coverage   99.74%   99.74%   +<.01%     
==========================================
  Files         160      160              
  Lines        2750     2751       +1     
==========================================
+ Hits         2743     2744       +1     
  Misses          7        7

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

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[levithomason]

Released in semantic-ui-react@0.79.0.