Fix: Correct browser unsaved changes warning

[shamoon]

Proposed change

This PR corrects an issue in 1.8.0 where the user was being shown a browser 'unsaved changes' after a document was opened, edited and then closed without saving. Video demonstrates the fix. As it turns out, this was not trivial. As always would welcome testing.

1366.mov

Fixes #1366

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other (please explain)

Checklist:

• I have read & agree with the contributing guidelines.
• If applicable, I have tested my code for new features & regressions on both mobile & desktop devices, using the latest version of major browsers.
• If applicable, I have checked that all tests pass, see documentation.
• I have run all pre-commit hooks, see documentation.
• I have made corresponding changes to the documentation as needed.
• I have checked my modifications for any breaking changes.

[qcasey]

Thanks for the fix, this works well in my testing

[github-actions]

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