Properly pass null exception to error handlers

[mbest]

Check for null or undefined error values before trying to access properties.

Fixes #3183

[domenic]

Thanks for working on this!

Per CONTRIBUTING.md, no new tests should be added to to-port-to-wpts/ (as that increases our porting burden). Instead, the test for the onerror handler should be added to the appropriate location in web-platform-tests/to-upstream, and the test for the virtual console behavior should be added to api/jsdom-errors.js

[mbest]

Can you tell me the appropriate location?

Per CONTRIBUTING.md, no new tests should be added to to-port-to-wpts/ (as that increases our porting burden). Instead, the test for the onerror handler should be added to the appropriate location in web-platform-tests/to-upstream, and the test for the virtual console behavior should be added to api/jsdom-errors.js

[mbest]

I think I got the right place. Let me know.

[domenic]

I've told GitHub to run the CI. I think it will fail on the lint in at least some cases.

Thanks for moving the tests. I think a better location for web platform tests would be html/webappapis/scripting/processing-model-2 (you'll need to create a couple folders), instead of dom/events. That's where existing tests for uncaught exceptions live in upstream.

[mbest]

Thanks for pointing out the lint issues. These are fixed now. I picked the WPT location based on a search for tests that involve throwing errors in an event handler. Although I see a lot of error-related tests in processing-model-2, I don't see any related to event handlers.

[TimothyGu]

@mbest As an example, https://github.com/web-platform-tests/wpt/blob/master/html/webappapis/scripting/processing-model-2/window-onerror-parse-error.html is a test that tests the window.onerror event handler.

[domenic]

Almost there :)

[TimothyGu]

Sorry, one last thing. Otherwise LGTM.

[mbest]

@domenic Anything else?