RangeError: Position X out of range (codemirror demo)

Getting the following error when there is no content after codemirror node view:

https://prosemirror.net/examples/codemirror/

resolvedpos.js:220 Uncaught RangeError: Position 26 out of range
    at Function.resolve (resolvedpos.js:220)

That was a bug in the demo. See this patch.

Thanks @marijn :pray: