Rectangle does not cover the entire ApplicationWindow

[Even if it seems duplicate, Can someone please mention a possible solution to this bug? Just closing the bug doesn't solve a user problem.]

In Qt5.9.2, I created a black rectangle inside a red ApplicationWindow for Samsung Note-5 with screen resolutions 1280*720, 1920*1080, 2560*1440 and Android-7.0 in two ways:

1. A rectangle having the same width and height of the ApplicationWindow
2. anchors.fill : parent

But in both ways the response is same - rectangle doesn't fill the entire ApplicationWindow. You can see about a pixel line on top side and about a pixel line on right side of the ApplicationWindow which is not filled. Even if I make a much larger Rectangle than the ApplicationWindow itself, I get the same output.

I noticed that If I try to nest rectangles and fill the parent rectangle with a child one then I get the completely filled parent rectangle without any issues.

Here I have attached a picture and a working project for testing.

QML Code:

import QtQuick 2.9
import QtQuick.Controls 2.2
import QtQuick.Layouts 1.3

ApplicationWindow {
    id: appWindow
    visible: true

    /* Developing mobile apps you don’t need to set width
       and height, because the ApplicationWindow always grabs
       the total available space.
    */

    color: "#ff0000" // Red color

    /* For some reasons I want this Rectangle here
     * and it MUST fill the entire window but I notice
     * a pixel or two line on top and right of the
     * screen.
     */
    Rectangle {
        width:  appWindow.width;
        height: appWindow.height

        //anchors.fill: parent // same output

        color: "#000000" // Black color
    }
}