Add TODO at site of exception from last crash

Crash on 2022-12-14 after resuming from hibernation showed a nil pointer
exception from a nil IView instance in FrOverview.pas

Author: delphidabbler

Src/FrOverview.pas

@@ -979,6 +979,7 @@ function TOverviewFrame.TTVDraw.IsUserDefinedNode(
   ViewItem: IView;  // view item represented by node
 begin
   ViewItem := (Node as TViewItemTreeNode).ViewItem;
+  // TODO -cBug: Exception reported as issue #70 seems to be triggered here
   Result := ViewItem.IsUserDefined;
 end;