Treat missing arguments to old BEAM block as a warning, or LOTS of tests (and presumably people's input files) fail.
Treat missing arguments to old BEAM block as a warning, or LOTS of tests (and presumably people's input files) fail.

SixTrack/SixTrack,SixTrack/SixTrack,SixTrack/SixTrack,SixTrack/SixTrack,SixTrack/SixTrack,SixTrack/SixTrack