Two ViewModel instances are created when the view has no field for the ViewModel

[manuel-mauky]

When using the CDI module under some conditions there are two instances of the ViewModel created when we would expect to have only one.

This sounds similar to #124

[manuel-mauky]

After a little investigation I found out that this is not a problem specific to CDI but in the main module.

When the View has no field defined for the ViewModel and no injection is happening, two instances of the ViewModel are created.

When a View is requested by the FXMLLoader we create a new ViewModel instance (or take one from DI) and are trying to inject it into the View. If the view has no Field defined for the ViewModel, nothing happens.
A view steps later we try to get the ViewModel instance from the View so we can provide it in the returned ViewTuple. If at this point there is no field in the View, we are creating a new ViewModel instance.

The solution is to create a new ViewModel instance in the ControllerFactory only when there is a Field defined.