Event dispatch fails after unmounting

[vsiao]

What is the current behavior?
Repro: https://jsfiddle.net/s8fg30fx/

• Click "Click Me!"
• Fails with "React DOM tree root should always have a node reference."

What is the expected behavior?
No failure, and event dispatch stops.

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?
15.3.1, Chrome 52+ OS X
Not certain if this has worked before.

Maybe related: #7103 and #7661

[zpao]

cc @spicyj @sebmarkbage

[sebmarkbage]

If you do this in the DOM you would get both events fired. Similarly if we defer DOM operations to a later schedule, that's also what would happen. I think that's the semantics we would want for this. Not a super high priority to fix this though.

The solution is to call event.stopPropagation(); in the inner handler.

[sophiebits]

Dupe of #3298 I guess.