doesn't work on firefox?

[GopherJ]

Describe the Bug

the same code panicked on chrome but not on firefox:

--headless --chrome => OK
--headless --firefox => KO, the tests passed without error, but actually it should panic

Steps to Reproduce

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

If applicable, add a link to a test case (as a zip file or link to a repository we can clone).

Expected Behavior

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Actual Behavior

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Additional Context

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