在调用roslaunch bringup racecar_gazeo.launch时, gazebo打开没有小车,出现以下三个错误: 1:[ERROR] [1628789648.863209787]: Failed to build tree: parent link [platform_link] of joint [camera_joint] not found. This is not valid according to the URDF spec. Every link you refer to from a joint needs to be explicitly defined in the robot description. To fix this problem you can either remove this joint [camera_joint] from your urdf file, or add "<link name="platform_link" />" to your urdf file. [robot_state_publisher-5] process has died [pid 2937, exit code 1, cmd /opt/ros/noetic/lib/robot_state_publisher/robot_state_publisher /joint_states:=/racecar/joint_states __name:=robot_state_publisher __log:= 2:[ERROR] [1628789669.000815, 89.792000]: Spawn service failed. Exiting.2Error [parser_urdf.cc:3193] Unable to call parseURDF on robot model Error [parser.cc:488] parse as old deprecated model file failed. 3:[urdf_spawner-4] process has died [pid 2936, exit code 1, cmd /opt/ros/noetic/lib/gazebo_ros/spawn_model -

预测是ROS版本的问题，我用的是ROS noetic 该怎样修改文件呢？