      */
     public var incrementButton:Button;
     
-    [SkinPart(required="true")]
+    [SkinPart(required="false")]
     
     /**
      *  A skin part that defines the  button that, 

 *  @productversion Flex 4
 */
[Event(name="change", type="flash.events.Event")]

/**
 *  @copy spark.components.supportClasses.GroupBase#style:focusColor

    //
    //--------------------------------------------------------------------------
    
    [SkinPart(required="false")]
    
    /**
     *  A skin part that defines the  button that, 
