The new handling of Client Buffer Integration causes a crash

I'm filing this bug upon another investigations done by my colleagues. The crash occurs with Qt which is build w/o "-opengl es2" configure option when running an app using Qt 3D on top of Qt Application Manager. The the below copy from emails with investigations done by gagi and see the links to the related issues:

when staring Neptune3 with "--verbose", it shows the following:

[*WARN*| qt.waylandcompositor.hardwareintegration] Failed to initialize
EGL display. Could not get EglDisplay for window.
[*WARN*| qt.waylandcompositor.hardwareintegration] Failed to initialize
hardware for client buffer integration: "wayland-egl"
[*WARN*| qt.waylandcompositor.hardwareintegration] No client buffer
integration was loaded, this means that clients will fall back to use
CPU buffers (wl_shm) for transmitting buffers instead of using zero-copy
GPU buffer hand
les. Expect serious performance impact with OpenGL clients due to
potentially multiple copies between CPU and GPU memory per buffer.
See the QtWayland readme for more info about how to build and configure
Qt for your device.

[*WARN*| default| qml-launcher] Failed to determine what client buffer
integration to use
[*WARN*| am.graphics| qml-launcher] Failed to create the global shared
OpenGL context.

So the problem is that because wayland-egl couldn't be initialized on
the compositor side, the client-side also cannot use it.

By explitly setting the client-buffer integration you can force the old
behavior:

QT_WAYLAND_CLIENT_BUFFER_INTEGRATION=wayland-egl QSG_INFO=1 ./neptune3-ui

A workaround for the issue could be to set the env variable in neptune3,
but i'm not sure whether this is really a good idea, especially as this
won't work on targets where a special client-integration is needed, e.g.
on imx6 targets.

The commit which introduced the change is the following:

commit 137966a6293b50f6b248d130a2e36e67df49335e
Author: Johan Klokkhammer Helsing <johan.helsing@qt.io>
Date: Tue Oct 22 13:41:49 2019 +0200