checks for NaN left/right position to ignore them

Just checked that it builds, but neither tested in a robot or gazebo.
Also, there's no test.

How can this be tested in gazebo?
How should we write a test for this?

To test on a robot, reboot the robot with the wheel's board disabled and check the odom topic and TF.
You shouldn't see any 'nan'.
Then, switch on the wheel's board and move the robot.
Now the odom topic and TF show change and you should see valid values, not 'nan'.