Unmount state fix

[xiaotian-tan]

I encountered issue when componentWillUnmount try to update active on undefined.

So I made small change to componentWillUnmount to make state updates safer.

A additional section in demo is added to demonstrate cached avatars as well.

[JorgenEvens]

Your issue would mean that unmount is called while the component is in a state transition, which should not happen. What version of React is this?

I'm afraid that by merging this PR we are bringing back the issue reported in #112. Let me try this out tonight and I'll let you know how it went.

[zedissime]

@JorgenEvens Any updates about this issue ?

[JorgenEvens]

@zedissime I only had a quick look and was unable to reproduce the issue described. Letting me know which version of React you are using and maybe a small reproduction case would be helpful.

[zedissime]

@JorgenEvens I'm facing it in React 16.3.2, I'll update it.
In my case, I have an customer index page with an avatar for each one.
I leave the page (with react-router-dom), and when I want to come back on the page, the error is thrown.

[JorgenEvens]

@zedissime Thanks, I'm gonna try reproduce this later today.

[zedissime]

Just in case of, I did update React in 16.4.1 and it is still happening.

[JorgenEvens]

@zedissime @xiaotian-tan @krue-doug I am unable to reproduce the issue, and I would really like to find out why componentWillUnmount is called before the state transition completes.

I've created a test-case on codesandbox, could you let me know if either the Toggle or Increment buttons trigger the above issue. And if not help me get a reproduction going here.

It broke 🎉

[JorgenEvens]

Managed to check that this does not bring back #112.

Thanks @xiaotian-tan for the bug report and @zedissime for some help on reproducing the issue.

[JorgenEvens]

This PR is released as part of v3.1.2.