Hi guys, I'm having troubles with introducing in my .world file a model found in Ignition Robotics. I am using Gazebo 11.2.0. In my case, I would introduce a some rocks in my world (the name of the model is Small Rock Fall). I searched for some hint and I've read that there is the possibility to introduce the model by using the following sintax:

<include>
<uri>https://fuel.ignitionrobotics.org/1.0/OpenRobotics/models/Small Rock Fall</uri>
</include>

However, if I load the .world file I get the following error message:

 [Msg] Downloaded model URL:
      https://fuel.ignitionrobotics.org/1.0/OpenRobotics/models/Small Rock Fall
 to:
      /home/simone/.ignition/fuel/fuel.ignitionrobotics.org/OpenRobotics/models/Small Rock Fall/2
 Warning [Model.cc:212] Non-unique names detected in XML children of model with name[small_rock_fall].
 [Err] [Plugin.hh:178] Failed to load plugin libignition-gazebo-breadcrumbs-system.so: libignition-gazebo-breadcrumbs-system.so: cannot open shared object file: No such file or directory
 [Err] [Plugin.hh:178] Failed to load plugin libignition-gazebo-breadcrumbs-system.so: libignition-gazebo-breadcrumbs-system.so: cannot open shared object file: No such file or directory
 [Err] [Plugin.hh:178] Failed to load plugin libignition-gazebo-breadcrumbs-system.so: libignition-gazebo-breadcrumbs-system.so: cannot open shared object file: No such file or directory
 [Err] [Plugin.hh:178] Failed to load plugin libignition-gazebo-breadcrumbs-system.so: libignition-gazebo-breadcrumbs-system.so: cannot open shared object file: No such file or directory
 [Err] [Plugin.hh:178] Failed to load plugin libignition-gazebo-breadcrumbs-system.so: libignition-gazebo-breadcrumbs-system.so: cannot open shared object file: No such file or directory
 [Err] [Plugin.hh:178] Failed to load plugin libignition-gazebo-breadcrumbs-system.so: libignition-gazebo-breadcrumbs-system.so: cannot open shared object file: No such file or directory
 [Err] [Plugin.hh:178] Failed to load plugin libignition-gazebo-breadcrumbs-system.so: libignition-gazebo-breadcrumbs-system.so: cannot open shared object file: No such file or directory

Can you help me, please? Thanks in advance.