Combobox popup overlaps the input box

Hi everyone,

I've noticed an annoying bug on Combobox component (zk6.5.8.1), which doesn't locate well the position of the popup when it's on the bottom of the window, and you type some word on the inputbox and then remove the entered words, the UI displays the popup overlap the inputbox, instead of display the popup above the inputbox.

I've been trying to override 'open' function with the position 'before_after', but I haven't had luck for now.

I've been able to recreate it on ZK-Fiddle

Thank you very much.