process has died during run the code --"roslaunch turtlebot3_follow_filter turtlebot3_follow_filter.launch"

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when i this website "https://mp.weixin.qq.com/s/pw9BX9KcOT..." to learn turtlebot related knowledge to ahieve robot following ,during i run the code "roslaunch turtlebot3_follow_filter turtlebot3_follow_filter.launch" .

i got this issue: “what():Character at element [6] is not valid in Graph Resource Name [~exist range 0.12 to 0.7 meter]. Valid characters are a-z, A-Z,0-9andlaser filter-2] process has died [pid 8635,exit code -6,cmd /opt/ros/melodic/lib/laser filters/scan to scan filter chain scan:=/scan scan filtered:=/scan filteredname:=laser filter log:=/home/chenqi/.ros/log/aoedb478-0f36-1lee-aec5-000c29ece332/laser filter-2.log].o file: home/chengi,ros/og/a0edb478-0f36-11ee-aec5-000c29ece332/laser filter-2*.log”

  the ubuntu version is 18.04 ros melodic)