解决运行gazebo时出现“[gazebo-2] process has died [pid 7920, exit code 255.....“的问题

在运行gazebo时，经常出现“[gazebo-2] process has died [pid 7920, exit code 255, cmd /opt/ros/melodic/lib/gazebo_ros/gzserver”，导致gazebo界面黑屏或出现一个空图，错误截图如下：

解决办法：使用Ctrl+C结束当前运行，然后输入

killall gzserver

再次roslaunch，问题解决。