B2017-179 detect if Paste/Replace was aborted due to Transition references and user had selected to go to the first transition that needs attention.

The Paste/Replace method can now return a NULL, so we needed to handle that.

PROMS/Volian.Controls.Library/DisplayTabControl.cs

@@ -527,6 +527,7 @@ namespace Volian.Controls.Library
 							break;
 						case ItemInfo.EAddpingPart.Replace:
 							EditItem ei = edtitm.PasteReplace(copyStartID);
+							if (ei == null) return false; //B2017-179 PasteReplace will return null if was aborted
               if (ei.MyItemInfo.ItemID != edtitm.MyItemInfo.ItemID)
               {
                 edtitm.Dispose();