The `reset` function is called inside `mj_resetData`, before any physics forwarding call has been made. It is therefore an error to read anything from mjData at this stage.
The only valid operation on mjData during `reset` is for a plugin to write into its own state variable slots and data struct. We modify the function signature to only provide access to these.
PiperOrigin-RevId: 495032492
Change-Id: Ic6d2967d2571a9083cbca1ba239ca70a8a51f474
Yuval Tassa