Bandbox: missing onBlur/onChange

Steps to Reproduce

run the attachment bug-unexpected-onchanging.zul

1. focus the bandbox-input -> onFocus event OK
2. type a few chars -> onChanging Event OK
3. open the bandbox dropdown -> onFocus event OK (kind of weird but ok)
4. click the white area next to the listbox -> no event OK
5. click outside the bandbox -> bandbox closes -> Missing onBlur and missing onChange event

Actual Result

Missing onBlur/onChange event

Expected Result

onBlur/onChange event

Debug Info

skipping step 4 (or clicking anywhere else inside the popup) doesn't cause the problem (onBlur and onChange are fired as expected)