unapply (handler) {
    super.unapply(handler, () => {
      if (!this.nextSibling) {
        console.error('Reference element was lost')
      }
      this.parent.insertBefore(this.elem, this.nextSibling) // Don't use `before` or `prepend` as `this.nextSibling` may be `null`
    })
  }
Re-adds the new element.
@param {module:history.HistoryEventHandler} handler
@fires module:history~Command#event:history
@returns {void}