Likely to happen when an element is empty, not just the editor, if you can get the cusros in an empty <p>, and press backspace you can get the same behavior, it can happen as you work on some content

Steps to reproduce:

1. Go to the Editor demo page http://demos.telerik.com/aspnet-ajax/editor/examples/overview/defaultcs.aspx in Chrome
2. CTRL+A on the editor and hit delete
3. Hit Delete or Backspace again

Result: Uncaught TypeError  Cannot read property 'nodeType' of undefined Appears in the console