listbox with a SimpleGroupsModel doesn't fire an expected onSelect event

Steps to Reproduce

1. run the attached zul
2. select group 1-option 2
or group 1-option 3
or group 2-option 1 (one of them)
and onSelect event is fired
3. select group 1-option 1

Current Result

the selection changed, but no firing onSelect event

Expected Result

fire onSelect event

Debug Information

1. it only happens right after you load the page, if you need to do the above steps again, you need to reload the page and do the steps to reproduce the bug.
2. if I select other items, the bug doesn't happen
3. I test with 9.6.0.FL.20210604-Eval, the bug still happens.