Created attachment 280836 [details]
The bad code probably responsible
It looks like we mistakenly try to index into a number, as in the screenshot, and we end up trying to create a DOMTreeElement with a null DOMNode. This eventually throws an exception which is dropped on the floor by DOMTreeManager._wrapClientCallback.
Created attachment 280839 [details]
Comment on attachment 280839 [details]
Clearing flags on attachment: 280839
Committed r201843: <http://trac.webkit.org/changeset/201843>
All reviewed patches have been landed. Closing bug.