Outline not rendered correctly in preview of default minimum Qt5.8 example

import QtQuick 2.8
import QtQuick.Window 2.2


Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")


    MainForm {
        anchors.fill: parent
        mouseArea.onClicked: {
            console.log(qsTr('Clicked on background. Text: "' + textEdit.text + '"'))
        }
    }
}

import QtQuick 2.8


Rectangle {
    property alias mouseArea: mouseArea
    property alias textEdit: textEdit


    width: 360
    height: 360


    MouseArea {
        id: mouseArea
        anchors.fill: parent
    }


    TextEdit {
        id: textEdit
        text: qsTr("Enter some text...")
        verticalAlignment: Text.AlignVCenter
        anchors.top: parent.top
        anchors.horizontalCenter: parent.horizontalCenter
        anchors.topMargin: 20
        Rectangle {
            anchors.fill: parent
            anchors.margins: -10
            color: "transparent"
            border.width: 1
        }
    }
}