The biggest trick here is the getter (QAbstractProxyModel::sourceModel),
which is returning nullptr, while internally using a global
staticEmptyModel() instance.
This lead to inconsistency while binding to a proxy model without
source model. The bound object would point to staticEmptyModel()
instance, while sourceModel() getter returns nullptr.
To solve this issue a custom QBindableInterface is implemented.
Task-number: QTBUG-85520
Change-Id: I597df891c7e425d51b55f50ccbacabdfe935cbac
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>
8161a9e5c0