Fix #607: bug in sprrznrc output of D/Dmax
Fix #607: bug in sprrznrc output of D/Dmax

Fix a bug in the sprrznrc output of D/Dmax vs radius. The indices of the
y coordinate and uncertainty were using the z index instead of looping
over the x index.

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