Cannot assign to .ctrl via named indexers

[saran-t]

Discussed in #237

^{Originally posted by DrawZeroPoint April 12, 2022}
Dear MuJoCo developers,

I am using the 2.1.4 version python binding of MuJoCo to control actuators with codes. So far, I encountered an odd issue that may be due to my improper way to use the API, so any suggestions are gratefully appreciated.

The simplified code I am using is like this:

actuator = self._data.actuator(actuator_name)
actuator.ctrl = cmd

where I can confirm that _data is initialized and contains the actuator; cmd is a plain float number. Oddly, the second line gives the error:

IndexError: too many indices for array: array is 0-dimensional, but 1 were indexed

I wonder if it is due to .ctrl should not be used in this way? What I planned to do is to assign the control value cmd to the actuator.
Previously with mujoco-py, I did the same thing like this:

self.sim.data.ctrl[actuator_id] = cmd
```</div>