Update RevDate to Today when RevNumber is changed

Handle using a TreeView that does not have a node selected

PROMS/VEPROMS User Interface/frmVEPROMS.cs

@@ -1255,7 +1255,12 @@ namespace VEPROMS
 		private void tc_SelectedDisplayTabItemChanged(object sender, EventArgs args)
 		{
 			// If the current procedure or section in the treeview doesn't match then change the treeview selection.
-			ItemInfo tvii = ((tv.SelectedNode as VETreeNode).VEObject) as ItemInfo;
+			//jcb added for error B2012-117
+			ItemInfo tvii;
+			if (tv.SelectedNode == null)
+				tvii = null;
+			else
+				tvii = ((tv.SelectedNode as VETreeNode).VEObject) as ItemInfo;
 			if (tc.SelectedDisplayTabItem == null) return;
 			if (tc.SelectedDisplayTabItem.MyItemInfo.IsProcedure)
 			{