B2018-097 handle a null reference when generating an enhanced document step tab.

PROMS/VEPROMS.CSLA.Library/Extension/ItemExt.cs

@@ -3735,8 +3735,8 @@ namespace VEPROMS.CSLA.Library
 				if (eds != null && eds.Count == 1 && eds[0].Type == 0)
 				{
 					ItemInfo srcItem = ItemInfo.Get(eds[0].ItemID);
-					return srcItem.MyTab.ToString();
-
+					if (srcItem != null) // B2018-097 handle a null reference
+						return srcItem.MyTab.ToString();
 				}
 				return null;
 			}