Fix some warnings when publishing with '-strict-publishing'

Signed-off-by: Erik de Bruin <erik@ixsoftware.nl>
If the view doesn't have cssData (as with the DataGridExample), this prevents an exception.

Signed-off-by: Erik de Bruin <erik@ixsoftware.nl>
Fix type checking: instanceof doesn't work with interfaces.

Signed-off-by: Erik de Bruin <erik@ixsoftware.nl>