   useEffect ->
     id2dom[message._id] = ref.current
     -> delete id2dom[message._id]
-  , [message._id, ref.current]
+  , [message._id]
   ## Scroll to this message if it's been requested.
   useEffect ->
     if scrollToLater == message._id

    slider.current.on 'change', (e) =>
      messageHistory.set message._id, diffs[e.newValue]
    messageHistory.set message._id, diffs[index]
  , [message._id, message.creator, message.created, input.current]

  <div className="historySlider">
    <input type="text" ref={input}/>

      nav.on 'affixed.bs.affix', affixResize
      nav.on 'affixed-top.bs.affix', affixResize
      undefined
    , []

    <nav className="contents" ref={ref}>
      <ul className="nav contents">
