Steps to reproduce

1. run the zul below

   <zk>
   	<combobox id="combo" autodrop="true" buttonVisible="false" autocomplete="false"/>
   	<button onClick="print()" label="print"/>
   	
   	<zscript><![CDATA[
   	    import org.zkoss.zul.ext.*;
   	    /*Dictionary.getDictionary() returns a String[] containing the dictionary words*/
   		ListModel dictModel= new SimpleListModel(Locale.getAvailableLocales());
   		combo.setModel(dictModel);
   		
   		public void print(){
   			System.out.println(((Selectable)autoCombo.getModel()).getSelection());
   		}
   	]]></zscript>
   </zk>
   

2. select the first item, ar_AE
3. delete the last 2 character, so it's ar_

result

About 0.5 sec, the input text becomes ar_AE again, the previously selected value.

expected result

like 7.0.6, the input text keeps unchanged after deleting the last 2 chars.

debug info

• 7.0.6 doesn't have such issue. After deleting the last 2 chars, the input text keeps unchanged.
• In 8.0, the au response contains selected item, selectedItemUuid_

  ....
  ['zul.inp.Comboitem','aCHPu',

  Unknown macro: {label}

  ,{},[]]],[
  ['zul.inp.Comboitem','aCHPv',

  Unknown macro: {label}

  ,{},[]]]]],["setAttr",[{$u:'aCHP0'},"repos",true]],["setAttr",[{$u:'aCHP0'},"selectedItemUuid_","aCHPh"]]],"rid":8}

  but 7.0.6 doesn't have.

• I think it relates to ZK-1987