Fix incorrect logic in ChAssembly::SearchMarker.
Fix incorrect logic in ChAssembly::SearchMarker.

Items of type ChBodyAuxRef are in the list of bodies, not in the list of "other physics items".  There is no need to traverse the latter list searching for markers.

armanpazouki/chrono,Milad-Rakhsha/chrono,Milad-Rakhsha/chrono,projectchrono/chrono,rserban/chrono,dariomangoni/chrono,rserban/chrono,armanpazouki/chrono,Milad-Rakhsha/chrono,armanpazouki/chrono,armanpazouki/chrono,dariomangoni/chrono,rserban/chrono,projectchrono/chrono,projectchrono/chrono,Milad-Rakhsha/chrono,Milad-Rakhsha/chrono,armanpazouki/chrono,projectchrono/chrono,dariomangoni/chrono,dariomangoni/chrono,projectchrono/chrono,projectchrono/chrono,rserban/chrono,dariomangoni/chrono,rserban/chrono,rserban/chrono,dariomangoni/chrono,armanpazouki/chrono,Milad-Rakhsha/chrono,rserban/chrono