Fix #612: throw an error for C >= 1 in DOSRZnrc
Fix #612: throw an error for C >= 1 in DOSRZnrc

Check for the validity of the path length biasing parameter C.
Previously the simulation would continue for C >= 1 with path length
biasing turned off.

MartinMartinov/EGSnrc,nrc-cnrc/EGSnrc,crcrewso/EGSnrc,MartinMartinov/EGSnrc,crcrewso/EGSnrc,nrc-cnrc/EGSnrc,mchamberland/EGSnrc,crcrewso/EGSnrc,crcrewso/EGSnrc,mchamberland/EGSnrc,nrc-cnrc/EGSnrc,crcrewso/EGSnrc,nrc-cnrc/EGSnrc,MartinMartinov/EGSnrc,MartinMartinov/EGSnrc,mchamberland/EGSnrc,mchamberland/EGSnrc,mchamberland/EGSnrc,mchamberland/EGSnrc,nrc-cnrc/EGSnrc,MartinMartinov/EGSnrc