Replace searching for constraint Bodies with corresponding PhysicalFrames (which includes Ground).
Replace searching for constraint Bodies with corresponding PhysicalFrames (which includes Ground).

opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core