Fix getLabelFromStackTrace edge case in Firefox

[srmagura]

What:

Closes #2614.

Why:

Invalid class names were causing styles to not be applied.

How:

Add new tests and make them pass.

Checklist:

• Documentation N/A
• Tests
• Code complete
• Changeset

[changeset-bot]

🦋 Changeset detected

Latest commit: abd7ad8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@emotion/react	Patch

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[codecov]

Codecov Report

Merging #2615 (be6a62d) into main (242f7d8) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head be6a62d differs from pull request most recent head abd7ad8. Consider uploading reports for the commit abd7ad8 to get more accurate results
| Impacted Files | Coverage Δ | |
|---|---|---|
| packages/react/src/get-label-from-stack-trace.js | 100.00% <100.00%> (ø) | |