Inverse Dynamics for Floating Base Robot Returns Nans

[dvedova]

Hello,

I am attempting to use the pybullet's calculateInverseDynamics() function for a floating base robot with 2 actuated degrees of freedom, but I am running into a couple of issues:

1. I expect the inverse dynamics to return a list of 8 joint torques, but when we call the function, it returns 9, which is confusing to me.
2. When I run the inverse dynamics function with the argument flag=1 the function returns a list of 9 "nans", instead of floats. Do you know why the function returns nans and not floats?
3. When I run the inverse dynamics function without the argument flag=1 then the function produces a warning message:
   b3Printf: Inverse Dynamics computations failed pybullet.error: Error in calculateInverseDynamics, please check arguments.

Attached is a simple test which reproduces these results. Please run 'PyBullet_Floating_2Dof.py' to reproduce the bugs.

Thank you in advance for any help you can provide.

bullet_issue_ID.zip