[next demo] Customized Snackbar clicking "Open Success Snackbar" gives runtime error

[bcjordan]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

Demo crashes and requests I report the issue here.

Expected Behavior 🤔

Demo does something after clicking

Steps to Reproduce 🕹

Steps:

1. Go to https://next.material-ui.com/components/snackbars/#customized-snackbars
2. Under Customized snackbars --> click Open Success Snackbar

Context 🔦

Want to see what Snackbar does in next.material-ui

Your Environment 🌎

Tech	Version
Material-UI	next (whichever is on next website)
Browser	Chrome

[oliviertassinari]

Seems related to #21811

[oliviertassinari]

I suspect an issue with react-transition-group, I didn't look deep, I have seen a few troubling behaviors.

[eps1lon]

I have seen a few troubling behaviors.

For example?

[oliviertassinari]

I have seen react-transition-group raise a warning about a wrong prop type HTMLElement vs HTMLDivElement, I don't see any structural difference between the demo and the others. Now, I didn't look deep, nor plan to. Forget my previous comment, it's noise :).

[eps1lon]

I have seen react-transition-group raise a warning about a wrong prop type HTMLElement vs HTMLDivElement

Where?

[oliviertassinari]

On the same page:

Which seems to be an issue with using iframe

[oliviertassinari]

Never mind, different problem https://github.com/reactjs/react-transition-group/pull/619#discussion_r420847211…