Check for a null when getting checkoff information

Added logic to use the DropCheckoff flag which tell the code that the checkoff goes on last row of the text. (default should be first row of text)

PROMS/Volian.Controls.Library/EditItem.cs

@@ -204,7 +204,7 @@ namespace Volian.Controls.Library
 			MyItemInfo.RefreshItemAnnotations();
 			ChangeBar = MyItemInfo.HasChangeBar;
 			CheckOff co = _MyItemInfo.GetCheckOffStep();
-			if (co != null)
+			if (co != null && co.UIMark != null)
 			{
 				UserCheckOff = true;
 				UserCheckOffChar = (char)co.UIMark;