我执行roslaunch mbot_gazebo view_mbot_gazebo_empty_world.launch

时出现

[gazebo_gui-3] process has died [pid 2460, exit code 134, cmd /opt/ros/melodic/lib/gazebo_ros/gzclient __name:=gazebo_gui __log:=/home/lxq/.ros/log/6686d262-e20f-11ea-91db-000c297cee3f/gazebo_gui-3.log].
log file: /home/lxq/.ros/log/6686d262-e20f-11ea-91db-000c297cee3f/gazebo_gui-3*.log

请问这是怎么回事呢