Some constructors for MultibodySystem did not create the default subsystem
Some constructors for MultibodySystem did not create the default subsystem

elkingtonmcb/simbody,chrisdembia/simbody,elen4/simbody,chrisdembia/simbody,elkingtonmcb/simbody,scamille/simbody,Gjacquenot/simbody,scamille/simbody,elkingtonmcb/simbody,chrisdembia/simbody,robojukie/simbody,simbody/simbody,simbody/simbody,robojukie/simbody,elen4/simbody,scamille/simbody,Gjacquenot/simbody,Gjacquenot/simbody,robojukie/simbody