If data missing from c3d file, return an empty table rather than throw exception downstream
If data missing from c3d file, return an empty table rather than throw exception downstream

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