OptionSelector components in flickable doesn't show its expansion

[Didier Roche-Tolomelli]

If a flickable only contains OptionSelector(s), the childrenRect isn't refreshed, and so, the options when expanding aren't shown.

For instance:
import QtQuick 2.4
import Ubuntu.Components 1.2

MainView {
    id: mainview
    objectName: "mainView"
    applicationName: "foo.bar"

    width: units.gu(40)
    height: units.gu(75)

    Page {
        title: "Settings"
        Flickable {
            id: flick

            anchors.fill: parent
            contentHeight: column.height

            Column {
                id: column
                width: flick.width

                OptionSelector {
                    text: i18n.tr("Label")
                    model: [i18n.tr("Value 1"),
                            i18n.tr("Value 2"),
                            i18n.tr("Value 3"),
                            i18n.tr("Value 4")]
                }
            }
        }
    }
}

A workaround is to set a Label after the OptionSelector with an empty space as a text:
                Label {
                    text: " "
                }