b22919543d
Before this change:
- User-modified values of `mjModel.stat.{meanmass, meaninertia}` would not be saved to XML.
- Non-user-modified values of `mjModel.stat.{meansize, extent, center}` would always get saved to XML.
After this change values are saved to XML only if provided by the user, either in the XML or by changing values in `mjModel` before saving.
PiperOrigin-RevId: 589473351
Change-Id: I4dcf4892ef61c35edf424226e731232d861bad8d