Rviz simulation robot model issue

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I am following the "mastering ROS for robotic programming" book and is currently doing the navigation stack. My gazebo results are correct, but there is an issue with the RViz simulation.

There is an error in the "robot model" of the RViz. Consider the error i am getting in the Rviz and the warning i am receiving with error in the terminal.

This problem is with many of the other results of Rviz, maybe i am missing an important concept here. Help me in this regard. Thank you Regards