gmx enemat segment faults
According to https://mailman-1.sys.kth.se/pipermail/gromacs.org_gmx-users/2018-May/120400.html it seems that gmx enemat is not robust to being supplied an energy file that does not have energygrps. It should give a graceful message that it can't do its job with such input.
Fixed enemat when .edr had no matching energy groups
Removed some debug output that obscured both the code and the useful
Used a simpler bool construct to decide whether to issue the warning.