listbox.getSelectedItem delivers wrong value with some GUI themes

Hello,
the listbox is defined as follows

<listbox id="lbFnct" mold="select" rows="1" />

When selecting an item in the listbox then a window containing the entries is falling down from the listbox. Now move the mouse pointer to an entry in the list. Afterwards leave that window without doing any click to the left or right. The selection window disappears. That entry is now displayed as the selected entry in the listbox. When you call now getSelectedItem or any other getSelection* method you get not the visible selected entry but the previously selected one.

This happens only with the themes breeze, sapphire, or silvertail. When using the theme atlantic it is not possible to leave the window with the listed entries.

Thanks in advance
Torsten