Check cssRules before css variables are read from stylesheet (again)

[floriangantner]

References

• Fixes blank page on certain browser plugins injecting stylesheets #2450

Description

check stylesheets in the dom before reading the css variables from them. If some error occurs reading the stylesheet cssRules (see the issue, f.e. it is some cross-origin stylesheet from some plugin which is not-readable) the exception is catched and the css variable not extracted from the stylesheet.

Instructions for Reviewers

see #2450 and #2557 and the previous PR #2454 for an overview over the discussion, especially the exception and the difference to the previous PR.

Include guidance for how to test or review your PR.

See the issue for details how to reproduce the bug with specific browser addons that inject stylesheets into the DOM.
Also login into the system (e.g. dspace sandbox) and see the admin sidebar if everything works (#2557) , especially by controlling the browser console for unexpected errors.

Checklist

This checklist provides a reminder of what we are going to look for when reviewing your PR. You need not complete this checklist prior to creating your PR (draft PRs are always welcome). If you are unsure about an item in the checklist, don't hesitate to ask. We're here to help!

• My PR is small in size (e.g. less than 1,000 lines of code, not including comments & specs/tests), or I have provided reasons as to why that's not possible.
• My PR passes ESLint validation using yarn lint
• My PR doesn't introduce circular dependencies (verified via yarn check-circ-deps)
• My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• My PR passes all specs/tests and includes new/updated specs or tests based on the Code Testing Guide.
• If my PR includes new libraries/dependencies (in package.json), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.
• If my PR includes new features or configurations, I've provided basic technical documentation in the PR itself.
• If my PR fixes an issue ticket, I've linked them together.

[tdonohue]

Thanks @floriangantner for the follow-up work! I'll give this a test myself in the next few days to verify it works & solves the issues that we previously ran into with #2454

[tdonohue]

👍 Thank you so much @floriangantner for sticking with this and finding a solution that works!

I reviewed/tested this today. I can verify it fixes the blank page bug when running Firefox + DarkMode extension. I can also verify that no errors are thrown in the DevTools Console. Also tested on Chrome and found no errors or issues there. Finally, I also verified that the #2557 bug (which was caused by the last version) does NOT exist in this PR. So, this now seems like a correct fix!

[dspace-bot]

Successfully created backport PR for dspace-7_x:

• [Port dspace-7_x] Check cssRules before css variables are read from stylesheet (again) #2589