Listbox's select mold issue on Firefox

Listbox中含有下拉選單Firefox瀏覽器中顯示異常之問題!
38版與42版
程式碼如下

<div>
 <listbox id="outListbox" height="450px" >
 <listhead>
 <listheader label="編碼" />
 <listheader label="測試" />
 </listhead>
 <listitem >
 <listcell label="1"></listcell>
 <listcell >
 <listbox mold="select" >
 <listitem >
 <listcell label="1"></listcell>
 </listitem>
 <listitem >
 <listcell label="2"></listcell>
 </listitem> 
 </listbox>
 </listcell>
 </listitem>
 <listitem >
 <listcell label="2"></listcell>
 <listcell >
 <listbox mold="select" >
 <listitem >
 <listcell label="1"></listcell>
 </listitem>
 <listitem >
 <listcell label="2"></listcell>
 </listitem> 
 </listbox>
 </listcell>
 </listitem>

</listbox>
 </div>

Steps to reproduce

1. load the zul above
2. click the select mold listbox inside a Listbox
3. move your pointer to select the drop-down listitem

Actual result

When a mouse pointer hovers out a Listitem, the drop-down list disappears immediately.

Debug information

• If outer listbox's listiem is selected, then the drop-down listbox inside that listitem can keep showing without disappearing when a mouse move to select one item.

Workaround

• <listbox id="outListbox" height="450px" nonselectableTags="">
• use <combobox> instead
• put the style below
  <style>
  /* a patch for select mold listbox under firefox*/
  .z-listitem:hover>.z-listcell { position:static; }

  </style>