fix(browser): log ErrorEvent.message when unhandled ErrorEvent.error is null

[hi-ogawa]

Description

Resolves #9285

This PR surfaces ErrorEvent.message on console, but notably this still keeps them as non unhandled errors.

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commit: b2fd44e

[Janpot]

Suggested change

	// `ErrorEvent` doesn't necessary have `ErrotEvent.error` defined
	// `ErrorEvent` doesn't necessary have `ErrorEvent.error` defined

[sheremet-va]

I don't see this being set anywhere?

[hi-ogawa]

This is for me to run test locally by BROWSER_NO_WEBKIT=1 pnpm -C test/browser ... commands as I cannot setup playwright on Archlinux.