[Rivet] MathUtils median falls over empty vector

[Holger Schulz]

Hi,

the Analysis ATLAS_2010_S8914702 calculates the median of a vector<double>

and currently segfaults if the vector is empty.


I don't know whether we should explicitly check the size of the vector or
return 0 in the median function --- not sure if the median of an empty set
is well defined though.


What do you think?

Holger