Fix libraries not being remembered when an unsaved library is discarded upon closing JabRef

[tomnguye]

Fixes #9190

Made it so that when closing the app if the focused database is not saved look for the first saved open database to set as focused.

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[koppor]

Seems like a (working) quick fix, but not solving the underlying issue. Maybe, the direction is more into the listeners. See #9238 for a discussion.

[tomnguye]

I think I need more information to go off of here. Could you describe how my implementation misses the underlying issue? otherwise what event do you feel requires listening?

[tomnguye]

I've made a change to the 'focused library' event listener that I hope better addresses the issue. Please point out if the revised fix has any issues

[koppor]

What happens at step 6 with your fix?

Maybe you can upload a video using Loom

[koppor]

This PR doesn't seem to fix the issue. See new comments at #9190 (comment).