Oberservable Preferences M (CleanupPreferences)

[calixtus]

Follow up to #9065

Will break the global preference settings for the cleanup jobs. User will have to reconfigure!
Migrations added!

• 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]

Tried it locally:

ERROR: Unexpected exception: java.lang.NullPointerException: Cannot invoke "java.lang.Boolean.booleanValue()" because the return value of "
java.util.Map.get(Object)" is null
        at org.jabref@100.0.0/org.jabref.preferences.JabRefPreferences.getBooleanDefault(JabRefPreferences.java:882)
        at org.jabref@100.0.0/org.jabref.preferences.JabRefPreferences.getBoolean(JabRefPreferences.java:874)
        at org.jabref@100.0.0/org.jabref.migrations.PreferencesMigrations.upgradeCleanups(PreferencesMigrations.java:482)
        at org.jabref@100.0.0/org.jabref.migrations.PreferencesMigrations.runMigrations(PreferencesMigrations.java:63)
        at org.jabref@100.0.0/org.jabref.gui.JabRefMain.start(JabRefMain.java:98)
        at javafx.graphics@18.0.2/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
        at javafx.graphics@18.0.2/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
        at javafx.graphics@18.0.2/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
        at javafx.graphics@18.0.2/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
        at javafx.graphics@18.0.2/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
        at javafx.graphics@18.0.2/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at javafx.graphics@18.0.2/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
        at java.base/java.lang.Thread.run(Thread.java:833)

[Siedlerchr]

When opening the cleanup dialog INFO: Doing a cleanup for 1 entries.. without having done anything

[Siedlerchr]

Works good so far