Topic /joint_states position show nan, and diff_drive_controller cannot work with it

[HappySamuel]

Hi

I found that the topic /joint_states position is showing [nan, nan], which eventually cause the diff_drive_controller cannot extract the position info to act on them, as per line 416 in diff_drive_controller , it will check the position by using isnan(lp) || isnan(rp), if nan, then will skip the codes below.

Is there a way to solve this?

Best,
Samuel