GUI remains black opening .world file containing "sun" as global light source

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Hi all,

I am using Gazebo 11. I have noticed that if I open a .world file containing sun as global light source, then the GUI remain completely black. The sun-light is added including the following lines in the .world file:

<include>
        <uri>model://sun</uri>
</include>

In particular, I am following the Velodyne tutorial.

When I run the file velodyne.world (here there is a link to the file C:\fakepathvelodyne.world), Gazebo opens but the screen remains totally black.

Using the command --verbose, I get the following error:

simone@gandalf:~$ gazebo -u /media/simone/velodyne/velodyne.world --verbose
Gazebo multi-robot simulator, version 11.0.0
Copyright (C) 2012 Open Source Robotics Foundation.
Released under the Apache 2 License.
http://gazebosim.org

[Msg] Waiting for master.
Gazebo multi-robot simulator, version 11.0.0
Copyright (C) 2012 Open Source Robotics Foundation.
Released under the Apache 2 License.
http://gazebosim.org

[Msg] Waiting for master.
[Msg] Connected to gazebo master @ http://127.0.0.1:11345
[Msg] Publicized address: 127.0.0.1
[Msg] Connected to gazebo master @ http://127.0.0.1:11345
[Msg] Publicized address: 127.0.0.1

(gzclient:1749): dbind-WARNING **: 15:06:21.767: Error retrieving accessibility bus address: org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files
[Wrn] [GuiIface.cc:119] QApplication: invalid style override passed, ignoring it.
[Wrn] [Publisher.cc:136] Queue limit reached for topic /gazebo/default/user_camera/pose, deleting message. This warning is printed only once.

If I don't add the sun to the .world file, I get the same identical error, but the simulation runs correctly and what I get in the GUI is a dark, but still "visible", scene:

How can I fix this issue? Thanks in advance!!!