Power Query List insert range at irregular intervals

Hi, I've pretty much got what I wanted , to insert a range at each change in list value, I did not want to group, and this is sort of grouping but not quite.

My problem is the last step i end up with a blank at bottom, witch is easy to remove but I'd rather it did not occur,

  let
  Source = {"A", "A", "A", "B", "C", "B", "B", "C", "C", "C", "D", "D", "D", "A", "B", "B", "D"}, 
  alist = Source, 
  dlist = List.Distinct(alist), 
  Generate = List.Generate(() => 0, 
    each _ < List.Count(dlist), 
    each _ + 1, 
    each let x = dlist{_}   in   List.Select(alist, (A) => A = x) ), 
  Insert = List.Transform(Generate, each List.InsertRange(_, List.Count(_), {""})), 
  Combine = List.Combine(Insert)
in
  Combine

I have tried to list.remvoe last within this but get an error, so any suggestions for that, and if there a better way's , I would be interested.

Richard.