title: dblookupcombobox has a null row
body: <p>I have a question about DBLookupComboBox.</p>
  
  <p>I have a program that has a database I wrote. It has everything, except when I open DBLookupComboBox it must have a row with null value for when user wants to select nothing. But there isn't one. How can I make a null row show up?</p>