Question: Plot fourier transform regardless if it is symbolically computable

I'm trying to plot the fourier transform of a function(a sigmoid) and maple refuses to plot it. It seems to try to compute it symbolically then craps out because it can't reduce it to a computable form. Of course trying to do some type of numerical evaluation is impossible because it substitutes the numerical value for the transform variable.

S := x->erf(x):

plot(abs(fourier(S(x),x,w)),w=0..100):

Warning, unable to evaluate the function to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct

Just want to plot the transform, I do not understand why it is do difficult for maple to do numerically. It should fall back on a numerical routine instead of crapping out.