Editors: Don't use model index outside of model/view.

The model index is an internal detail of the model/view and shouldn't be
used outside that context.

Change-Id: I2c1f742fff427484f6ff244dd3e0d8428a7318d3
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>