Regression in QQmlPropertyMap when used as sibling and inserting properties very late

Qt 5.2 RC1 breaks some plugins like https://code.launchpad.net/gsettings-qt
In Qt 5.1.1 they work as expected but reading properties always results in
"Unable to assign [undefined] to QString"

but inside of the Component it works.

How to reproduce (Linux only):
bzr branch lp:gsettings-qt
qmake && make && make install

import QtQuick 2.1
import QtQuick.Controls 1.0
import GSettings 1.0
import QtQuick.Layouts 1.0
import QtQuick.Dialogs 1.0

ApplicationWindow {
width: 300
height: 100

GSettings

{ id: test schema.id: 'org.gnome.desktop.interface' }

Text

{ id:text text: test.toolbarStyle }

}

The above works in Qt 5.1.1 and I have also seen similar behavior in other plugins