Crash in constructor of RooNLLVar

When calling the RooNLLVar constructor with passing a RooCmdArg defining the conditional or projected observables using a RooCmdArg the function
(line 58 of RooNLLVar.cxx)

RooCmdConfig::decodeObjOnTheFly("RooNLLVar::RooNLLVar","ProjectedObservables",0,&_emptySet ,arg1,arg2,arg3,arg4,arg5,arg6,arg7,arg8,arg9)

returns a null pointer.
See the attached macro to reproduce the problem (from
http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=18903 )