[Reg5.14->5.15.1]Item selection in Custom popup menu in QComboBox stopped working in 5.15.1

if menu item is added and shown via re implementing showPopup() of QComboBox, item selection via mouse does not work.
Attached example with following steps can be used to see it.
Run example
Menu:File -> TestDialog will show dialog, click on combobox and try to select any of its item using mouse it wont select any item,
Using up/dwn arrow works