Unclear if error event from "update the image data" matches implementations

Attempting to verify the behaviour of step 10 of update the image data, I ran this test in Firefox, Safari, and Chrome on macOS. Each browser only displayed "error1". As far as I can tell img elements with either a srcset attribute or a picture parent should cause the algorithm to be invoked, and then end up with a null selected source. This doesn't appear to match the behaviour of any browser I've tried, however.

cc @zcorpan