title: blank option in drop down disappears from custom Sharepoint list
body: <p>I have a custom list template that is deployed as a .wsp.  The list has almost 30 columns, including several DropDownLists of column type "Choice".  None of the columns are required and the customer wants a blank option as the default selection for each.  Unfortunately once the list item has been saved, any columns that have had values selected can no longer be un-selected.</p>
  
  <p>To get around this we added a blank &lt;CHOICE&gt; &lt;/CHOICE&gt; element in the schema.xml and event.xml files.</p>
  
  <p>Unfortunately, one of the columns completely ignores the blank choice - acts just the same as I described above (SP default behavior).  I have already checked the obvious (to me) things - making sure guids match up, the blank choice exists in both files, etc.</p>
  
  <p>Any other ideas on what I can look into to fix?</p>