JavaScript debugger: Expression evaluators disappear when stepping

1. Open project qtdeclarative\examples\quick\demos\samegame\samegame.qmlproject from Qt5's repository.
2. Set a breakpoint at the first line of function startNewGame(gc, mode, map).
3. Run the project in debugger.
4. In the app click "1 Player".
   The breakpoint is being hit.
5. In "Locals and Expressions" view, right-click "this" and select "Add Expression Evaluator for 'this'" from the context menu.
   An expression evaluator for "this" will be added in the lower part of the "Locals and Expressions" view. It's not useful, but that is QTCREATORBUG-13474.
6. Step over
   The expression evaluator disappears.
7. Expand the tree elements or "this".
   The expression evaluator shows up again.

Expression evaluators should remain visible when stepping.