Fix IE8 potentially throwing during restoreSelection

> Can't move focus to the control because it is invisible, not enabled, or of a type that does not accept the focus.

I'm unable to reproduce this separately because I don't really understand the cause. I have a custom implementation of a drop-down used in a custom popup, when you click on the drop-down (just divs) it expands and shows a list of items (just more divs). When the drop-down is closed the above error is thrown in `focusNode()`, called by `restoreSelection()`, only IE8 AFAIK.

If I delay the closing of the drop-down (which is litterally just setting `this.state.open` to false and not rendering it), the error still occurs. I do *nothing* except set the state to closed. Nor do I in any way force focus when it's opened.

Not fixed in master.