Check list property before component when validating bindings

There are lists that won't accept a component as element. For example
QQuickItem's children will only accept QQuickItems.

Task-number: QTBUG-41848
Change-Id: I0fc7b0d1a4770d596caf681be92dff216f48d32b
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>