Avoid wrong contact update into the model.

Change-Id: Ia8dbcdec96a5f7b25842f76c6b1aae46c5553c3e
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Christopher Adams <chris.adams@jollamobile.com>