title: Flex AdvancedDataGrid with Grouping, how do I get objects to appear under first GroupingField if the second GroupingField is null?
body: <p>I am using an AdvancedDataGrid with two GroupingFields. The dataProvider has a list of objects with these two field values, but occasionally the second field value can be null. When it loads, the AdvancedDataGrid UI has a root folder (first GroupingField) and some additional subfolders (second GroupingField). This is all good. However, the objects with a null value for the second GroupingField, just get placed in a subfolder with no label.</p>
  
  <p>I want the objects with a null second GroupingField value to appear as leaf nodes beneath the root folder (first GroupingField) minus the blank subfolder.</p>
  
  <p>A good way to picture this would be a file explorer. Is there a good way to do this? Make the folder icon disappear maybe after expanding this node through actionscript?</p>
  
  <pre><code>ParentFolder
     SubFolder
        Leaf Object
        Leaf Object
     SubFolder
        Leaf Object
     Leaf Object
     Leaf Object
  </code></pre>