[Rivet] turn off "Event beams mismatch error"

[Fabio]

Hi,

I'm running an analysis of events generated by JEWEL and my data has 
beams of different types. I'm running Rivet 3 and using the option 
--ignore-beams, but the beam check doesn't want to accept my data. How 
can I get around this?

Cheers,

Fabio Canedo