Removed extraneous if-statement within double loop.

            // -> no point to start i at 0, start from jmin:

            size_t jmin = (k >= pulse.size() - 1) ? k - (pulse.size() - 1) : 0;

            for(size_t i = jmin; i <= k; ++i) {

                if((k - i) < pulse.size()) {

                outsum += pulse.at(k - i) * impulse_response_function_.at(i);

            }

            }

            amplified_pulse.addCharge(outsum, timestep * static_cast<double>(k));

        }