Modulation on flattop distribution creates a gap

Summary

When introducing a modulation in the flattop distribution, there is a gap between the end of t_flattop and t_rise. This is because the flat part is mistakenly displaced. The line t += sigmaTFall_m * cutoffR_m[2]; is missing.

Steps to reproduce

Flattop distribution with

        FTOSCAMPLITUDE = 50,                                                                                                                           
        FTOSCPERIODS = 7,  
        WRITETOFILE = True,

Then look at the particle distribution along the longitudinal axis