websocket: Frontend freezes when `ob run` reloads

This happens only in GHC/jsaddle, and not GHCJS/javascript.

For the example app, when using the websocket route, the frontend will completely freeze (you can't even select text with mouse) right after `ob run` reloads. You have to kill the browser tab, and open it again. 

The full GHCJS build does not suffer from this problem. 