In this codepen: https://codepen.io/kphillips86/pen/jOOdpYo?editors=0010, if you change filter from "e" to "", this error is thrown:

Uncaught TypeError: Cannot read property 'nextSibling' of undefined

This happens because the parsedFilteredItems property changes once because it directly listens on filter and also changes because filteredItems changes when filter changes. Both of these changes cause the items to be removed from the list in one flush of the NOTIFY queue.