Fix second_der calculation

src/components/pulses/generic_pulses.jl

@@ -113,6 +113,9 @@ function split_timestep(gp::GenericPulse, precision)
         max_second_der = 0.
         for index in 2:length(arr)-1
             poly = fit(gp.time[index-1:index+1], arr[index-1:index+1])
+            if iszero(length(poly.coeffs))
+                continue
+            end
             second_der = abs(poly.coeffs[end])
             if second_der > max_second_der
                 max_second_der = second_der