Visibility: an update after component's unmount throws exception

[VikVelev]

The responsiveness on your doc page was broken and wasn't considering devices other than mobile and desktop.

Fixes #2570

[welcome]

💖 Thanks for opening this pull request! 💖

Here is a list of things that will help get it across the finish line:

• Run yarn lint locally to catch formatting errors. This will fix some errors automatically, commit and push any changes.
• Run yarn test locally to catch errors. This ensures all components still behave as they should.
• Run yarn start to run the doc site locally and try a few pages, ensuring everything is in good working order.
• Include tests when adding/changing behavior.

We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[codecov-io]

Codecov Report

Merging #2571 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2571   +/-   ##
=======================================
  Coverage   99.74%   99.74%           
=======================================
  Files         160      160           
  Lines        2744     2744           
=======================================
  Hits         2737     2737           
  Misses          7        7

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[layershifter]

To team: don't merge this, the problem is in suddenly unmounted Visibility component and should be fixed there.

[levithomason]

@layershifter Can you take a look here?

[levithomason]

I'm not sure on this. The props being spread in Responsive.onlyComputer include a minWidth of 992. Why is is that we need to override this to 768?

Semantic-UI-React/src/addons/Responsive/Responsive.js

Line 56 in 8ccee0f

static onlyComputer = { minWidth: 992 }

If 768 is indeed correct, then we should not be spreading the other value and then overridding it.

[levithomason]

This one also is specifically spreading a different value for minWidth. Why is it that we need to override this to 0?

Semantic-UI-React/src/addons/Responsive/Responsive.js

Line 54 in 8ccee0f

static onlyMobile = { minWidth: 320, maxWidth: 767 }

As above, if minWidth 0 is correct then we should not be spreading onlyMobile here, or, we need to update the values of onlyMobile.

[layershifter]

See #2635 for details.