Added logic to protect against failures when an invalid transition text is removed.

Added logic to protect against failures when an invalid transition text is selected.

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

@@ -497,6 +497,9 @@ namespace VEPROMS.CSLA.Library
 		}
 		private static string BuildString(TransitionBuilder tb)
 		{
+			//Invalid Transition Check
+			if (tb._ToItem.ActiveParent == null || tb._RangeItem.ActiveParent == null)
+				return "?";
 			int startIndex = 0;
 			int index = -1;
 			string prefix = null;