Let tests fail if there is a javascript error

[rodja]

Motivation

As @evnchn discovered in #5143, current screen tests let javascript errors slide.

Implementation

Simple addition to the teardown of screen which checks for javascript errors.

Progress

• I chose a meaningful title that completes the sentence: "If applied, this PR will..."
• The implementation is complete.
  • fix tests which have js errors (if any)
• More Pytests are not necessary.
• Documentation is not necessary

[evnchn]

Need to merge #5143 first. The logs are crazy right now.

But we still have 2 other errors:

2025-09-16T08:55:00.0333110Z ERROR tests/test_echart.py::test_update - Failed: JavaScript console errors:
2025-09-16T08:55:00.0334500Z [{'level': 'SEVERE', 'message': "http://localhost:3392/_nicegui/2.24.1.dev0/static/vue.global.prod.js 4:16598 TypeError: Cannot read properties of undefined (reading 'length')\n    at Proxy.update_chart (http://localhost:3392/_nicegui/2.24.1.dev0/components/2d17e85f29692e468dca813727906fdd/echart.js:97:111)\n    at Proxy.mounted (http://localhost:3392/_nicegui/2.24.1.dev0/components/2d17e85f29692e468dca813727906fdd/echart.js:82:10)", 'source': 'console-api', 'timestamp': 1758012718754}]
2025-09-16T08:55:00.0334708Z ERROR tests/test_element.py::test_invalid_tags - Failed: JavaScript console errors:
2025-09-16T08:55:00.0336004Z [{'level': 'SEVERE', 'message': "http://localhost:3392/_nicegui/2.24.1.dev0/static/vue.global.prod.js 4:74775 Uncaught DOMException: Failed to execute 'createElement' on 'Document': The tag name provided ('🙂') is not a valid name.", 'source': 'javascript', 'timestamp': 1758012748132}]

[evnchn]

hmm. Flaky test?

[evnchn]

Maybe re-run the test? Hmm I still don't get why all fails so disasterously.

Also maybe in alignment with #5153 we can target 3.0? "Unfair" if we rid all pytest warnings but not all JS errors?

[evnchn]

It's been a month and we have #5225 which you can write to.