Hangs on `<div dangerouslySetInnerHTML={{__html: undefined}} />`

[toddw]

We had a situation where the html trying to set ended up being undefined. I would expect this to throw a warning but still render like react-dom does. Instead it just hangs. This was really tricky to track down but we eventually traced it back to react-dom-stream acting differently than react-dom when html happens to be undefined.