CollaborationAvatarGroup grows larger and larger on idle

[wfischlein]

When leaving the browser window open (e.g. over night) that shows a CollaborationAvatarGroup then the number of avatars just grows

Steps to reproduce the behavior:

• set up a spring-boot project with a view that shows a CollaborationAvatarGroup
• put 'server.servlet.session.timeout=30' into the application.properties
• run project and open that view
• wait for at least 30 seconds
• see more than one avatar even when only one UI is open
• in log, see entries like this:

Exception in thread "pool-1-thread-3" Exception in thread "pool-1-thread-9" Exception in thread "pool-1-thread-4" com.vaadin.flow.component.UIDetachedException at com.vaadin.flow.component.UI.handleAccessDetach(UI.java:415) at com.vaadin.flow.component.UI.access(UI.java:515) at com.vaadin.flow.component.UI.access(UI.java:502) at com.vaadin.collaborationengine.ComponentConnectionContext.lambda$flushPendingActionsIfActive$1(ComponentConnectionContext.java:290) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base/java.lang.Thread.run(Thread.java:834)

Expected behavior Avatar group should stick to the size of open UIs, log should not show stacktraces

Screenshots

Versions

• Vaadin version: 23.0.0.alpha2
• Collaboration Engine version: 5.0.0.alpha1
• Java version: 11
• OS version: MacOS 12.0.1

Additional context Add any other context about the problem here.